Egg-free custards and puddings: cornflour, agar, plant milk
A classic custard thickens because egg yolk proteins set as they heat, giving richness, body and a glossy finish. Without eggs, something else has to do the thickening. The usual choices are cornflour (called cornstarch in the US), custard powder, agar for a firm set, and blended silken tofu for baked fillings. Each gives a different texture, and the plant milk you choose changes the result too. This guide explains how to thicken with each, how to avoid lumps and skin, which plant milks suit custards and puddings, and how to fix the usual problems. It builds on our guides to thickeners and gelling agents rather than repeating them.
Four ways to thicken or set
| Method | How it works | Texture | Best for | Watch for |
|---|---|---|---|---|
| Cornflour (cornstarch) | Starch swells and thickens when heated in liquid | Smooth, creamy, spoonable; firmer when chilled | Pouring custard, pastry cream, spoonable puddings | Lumps if added to hot liquid; thins if boiled hard for long or with much acid |
| Custard powder | A packet mix, traditionally cornflour with flavour and colour | Smooth, yellow, familiar | Quick pouring custard, trifle, custard tarts | Ingredients differ by product and country; check the label |
| Agar | A seaweed gel that sets firm as it cools | Firm, clean-cutting, can be blended smooth | Moulded puddings, panna cotta-style desserts, set tart fillings | Must be boiled to dissolve, and sets quickly once cool |
| Silken tofu | Blended tofu protein, usually with a little added starch, that firms on baking or chilling | Dense, creamy, set | Baked tart and pie fillings, chilled puddings | Needs thorough blending and a tasty base to hide any bean flavour |
Cornflour custard
The method is the same as for any starch sauce. Mix the cornflour with a few spoonfuls of cold plant milk until smooth. Warm the rest of the milk with the sugar until it steams, then whisk the paste in and keep stirring while the mixture comes up to a gentle simmer and thickens. Cook for a minute or two longer, so the starch is cooked through and no raw taste is left, then take it off the heat.
As a starting point, 1 tablespoon of cornflour per cup (240 ml) of liquid gives a light pouring custard and 2 tablespoons gives a thick, spoonable pudding, which matches the ratios in our thickeners guide. Unmoulded puddings need more starch, and amounts vary between recipes, so follow a tested recipe or switch to agar. Vanilla gives the classic flavour. A pinch of turmeric can add an egg-yolk colour without much taste. Cornflour custard has less richness than egg custard, so a spoonful of coconut cream, a little cashew cream or a small knob of vegan butter helps.
Custard powder: check the label
In the UK and several other countries, custard powder is a long-established egg-free product: mostly cornflour with flavouring and colouring. You stir it with cold milk and sugar, then heat it. But formulations differ between brands and countries, and some products contain milk-derived ingredients or other additives, so read the ingredient list for vegan and gluten-free needs. Instant pudding mixes in the US are a different product again and can contain milk ingredients, so do not assume they suit vegan cooking. In some countries, including Australia and New Zealand, a product sold as cornflour can be made from wheat, so check that it is made from maize if you avoid gluten.
Agar and silken tofu
Agar makes puddings that hold a shape: dissolve it in the plant milk, boil it, then sweeten, flavour and pour into moulds. The ratio per cup, the boiling time and the blend-and-reset trick for a creamy texture are in our guide to vegan gelatin substitutes, so they are not repeated here.
Silken tofu blended until completely smooth with plant milk, sugar, vanilla and a little starch makes a filling that firms as it bakes or chills. It suits pies and tarts. Blend it for longer than seems necessary, and use plenty of vanilla or spice.
Which plant milk suits
| Plant milk | Suits | Notes |
|---|---|---|
| Soy milk (unsweetened) | Most custards and puddings | Neutral flavour and good body. Can curdle if combined with acidic fruit while hot. |
| Oat milk | Pouring custard, rice-style puddings | Naturally slightly sweet and creamy. Some thicken more than others when heated. Choose a gluten-free label if needed. |
| Full-fat coconut milk | Rich puddings, set desserts | Adds richness and a coconut flavour; stir well, because in many cans the cream and water separate. |
| Almond milk | Light puddings | Thinner and nutty; may need a little more starch or a spoonful of fat. |
| Rice milk | Light puddings | Thin and sweet; gives a looser set. |
| Cashew or pea milk | Creamy puddings | Pea milk is high in protein; flavours vary by product. |
Unsweetened, plain or vanilla versions are the safest choice, since sweetened and flavoured milks change the sugar balance. Heat all plant milks gently. Our plant milks guide covers more on how they behave when cooked.
Skin, lumps and other problems
A skin forms because the surface dries out and the proteins and starch there concentrate. Soy milk forms a particularly clear skin when heated. Press baking parchment or cling film directly onto the surface while the pudding cools, or stir occasionally as it cools.
| Problem | Likely cause | Fix |
|---|---|---|
| Lumps | Cornflour added to hot liquid, or not whisked | Mix with cold milk first, whisk constantly, and sieve if needed. |
| Too thin | Too little starch, or it was not cooked long enough | Simmer a little longer, or thicken with a small extra slurry. |
| Thin after cooling | Overcooked starch breaking down, or acidic fruit added hot | Cook gently and fold in acidic fruit after cooling. |
| Tastes raw or floury | Starch not cooked through | Cook for another minute or two. |
| Skin | Surface drying as it cools | Press film or parchment onto the surface. |
| Scorched bottom | Heat too high or no stirring | Use a heavy pan, low heat and constant stirring. |
| Watery after freezing | Starch gels release water when thawed | Avoid freezing starch puddings; keep them chilled instead. |
| Will not set in a tart | Starch-thickened custard needs to cool | Chill until firm before slicing. |
Labels and allergies
Maize cornflour, agar and most plant milks are gluten-free by nature, but a product sold as cornflour can be wheat-based in some countries (see above), oat milk is only gluten-free when labelled so, and processing and packing differ, so check every label. Soy, tree nuts, oats and coconut are common allergens or sensitivities, and which count as allergens varies by country. For coeliac disease or any allergy, rely on the label and talk to your doctor or dietitian.
What this guide is based on
- That egg yolk proteins set custard, and that starch thickens by swelling when heated, is general cooking knowledge.
- The ratios of 1 and 2 tablespoons of cornflour per cup (240 ml) and about 1 teaspoon of agar powder per cup are commonly published rules of thumb, shared with our thickeners guide. They are not from our own testing, and packet instructions should be followed first.
- The remarks on custard powder and instant pudding mixes are general and differ by country and product. We name no brands, and the label is the authority.
- The plant milk notes reflect common cooking experience, not our own side-by-side tests. Products vary.
- Allergy and gluten remarks are general. Check labels and ask a doctor or dietitian.