Before you start
Birthday cake as a cookie: soft, thick, vanilla-forward, and visibly celebratory. The texture secret is cornflour in the dough and a deliberate underbake, which keeps them pillowy for days. Use the long jimmies-style sprinkles. The tiny round hundreds-and-thousands bleed their colour into the dough and turn it grey.
Everything you need
- ¾ cup (170 g) unsalted butter, soft
- ¾ cup (150 g) granulated sugar
- 1 + 1 egg, plus 1 yolk
- 1 tbsp vanilla extract
- 2 cups (250 g) all-purpose flour
- 2 tsp cornflour (cornstarch)
- 1 tsp baking powder
- ¼ tsp baking soda
- ½ tsp fine salt
- ½ cup rainbow sprinkles (jimmies)
Weigh, don't scoop. Measuring flour by cups can overpack it and dry out your bake. Tap any ingredient to open its converter.
Method
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Beat the butter and sugar until very pale and fluffy, 3 full minutes. This aeration is the lift these cookies rely on.
For this step
- ¾ cup (170 g) unsalted butter
- ¾ cup (150 g) granulated sugar
-
Beat in the egg, yolk and the vanilla. A whole tablespoon of vanilla is correct: it's the birthday flavour.
For this step
- 1 tbsp vanilla extract
-
Fold in the flour, cornflour, baking powder, baking soda and salt until nearly combined, then fold in the sprinkles with three or four strokes only.
For this step
- 2 cups (250 g) all-purpose flour
- 2 tsp cornflour (cornstarch)
- 1 tsp baking powder
- ¼ tsp baking soda
- ½ tsp fine salt
- ½ cup rainbow sprinkles (jimmies)
-
Chill the dough 45 minutes. Heat the oven to 180°C / 350°F and line two trays.
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Roll into 18 balls and press a few extra sprinkles onto the tops. Bake one tray at a time for 9 to 10 minutes, until the edges are just set and the tops still look pale and underdone.
For this step
- ½ cup rainbow sprinkles (jimmies)
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Rest on the tray 10 minutes. Pale and puffed is the finish line. Golden brown means birthday biscuits, which is a different, sadder thing.
Baker's tips
- Minimal folding once the sprinkles go in. Overmixing streaks their colour through the dough.
- These cookies should never brown beyond the faintest gold at the edge. Set a timer for the low end and trust the rest.
Make it your own
- Fold in ½ cup of white chocolate chips alongside the sprinkles.
- Sandwich two cookies around vanilla buttercream for a birthday cookie sandwich.
Storing & freezing
Airtight for 5 days, staying soft thanks to the cornflour and underbake. Dough balls freeze for 3 months.
Frequently asked
What sprinkles are best for baking into cookies?
Long waxy jimmies. They hold their colour and shape in the oven. Nonpareils (tiny balls) bleed dye into the dough, and sugar strands dissolve entirely.
Why put cornflour in cookie dough?
A small amount softens the gluten structure, giving a more tender, thick-set crumb. It's the same trick shortbread pulls with rice flour.
Baking in a different unit? Use the cups ↔ grams converter or the recipe scaler to halve or double this recipe.
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A note on cooking safely. Recipes are provided for informational purposes only and are not medical or nutritional advice. Cooking times, temperatures and quantities are suggestions: use your own judgement, and check that meat, poultry, fish and eggs are properly cooked before serving.
Consult a qualified healthcare professional before making dietary changes, particularly if you have allergies, a medical condition or specific nutritional requirements.