Cookie butter brings caramel, cinnamon and a little smokiness, so these blondies taste far more complex than the short ingredient list suggests. Warm the spread before you swirl it. Cold cookie butter sits in lumps instead of marbling.
Everything you need
- ¾ cup (170 g) unsalted butter, melted
- 1¼ cups (275 g) light brown sugar, packed
- 2 large eggs
- 2 tsp vanilla extract
- 1½ cups (188 g) all-purpose flour
- ¾ tsp fine salt
- ½ tsp ground cinnamon
- ½ cup (135 g) cookie butter (Biscoff spread)
- ¾ cup (128 g) white chocolate chips
- ½ cup (50 g) Biscoff biscuits, crushed
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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Heat the oven to 175°C / 350°F. Line a 20 cm / 8 inch square tin with baking paper, leaving an overhang so you can lift the slab out later.
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Whisk the melted butter and brown sugar together hard for a full minute, until glossy. That minute is what gives blondies their shiny, papery top.
For this step
- ¾ cup (170 g) unsalted butter
- 1¼ cups (275 g) light brown sugar
- ½ cup (135 g) cookie butter (Biscoff spread)
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Whisk in the eggs and vanilla, then fold in the flour, salt and cinnamon until just combined. Fold through the white chocolate chips.
For this step
- 2 large eggs
- 2 tsp vanilla extract
- 1½ cups (188 g) all-purpose flour
- ¾ tsp fine salt
- ½ tsp ground cinnamon
- ¾ cup (128 g) white chocolate chips
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Scrape into the tin and level the top. Warm the cookie butter for 15 seconds in the microwave so it pours, then dot spoonfuls over the batter.
For this step
- ¾ cup (170 g) unsalted butter
- ½ cup (135 g) cookie butter (Biscoff spread)
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Drag a knife through in an S shape, three or four passes only. Over-swirling turns the marble into mud. Scatter the crushed biscuits over the top.
For this step
- ½ cup (50 g) Biscoff biscuits
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Bake for 26 to 30 minutes, until the edges are set and the middle still has a slight wobble. Cool completely in the tin before slicing, or they'll fall apart.
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Worth knowing
- Underbaking slightly is the whole point of a blondie. A skewer should come out with moist crumbs, not clean.
- Chilling the cooled slab for an hour before slicing gives clean edges and a fudgier bite.
Make it your own
- Swap the cookie butter for the same weight of peanut butter or Nutella.
- Add 100 g chopped pecans with the white chocolate for crunch.
Storing & freezing
Airtight at room temperature for 5 days, or freeze the cut squares for 3 months. They eat well cold, straight from the fridge.
Frequently asked
How many grams is half a cup of cookie butter?
About 135 g. It's denser than peanut butter, so scoop it level rather than heaped if you are measuring by cup.
Why are my blondies cakey instead of fudgy?
Usually too much flour or too long in the oven. Weigh the flour if you can, and pull the tin while the centre still wobbles.
Cooking 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.