Spoon Biscoff spread into thick discs (about 1/2 inch thick) on a parchment-lined plate.

Freeze for at least 1 hour until firm.

Add butter to a saucepan over medium-high heat.

Cook, stirring occasionally, until foamy with golden brown specks and a nutty aroma (about 4–5 minutes).

Immediately pour into a heatproof bowl and cool to room temperature.

In a bowl, whisk together flour, cornstarch, baking powder, baking soda, salt, and spices.

Stir sugars into cooled browned butter.

Add egg, egg yolk, and vanilla, mixing until smooth and caramel-like.

Add dry ingredients and mix until mostly combined.

Fold in white chocolate chips.

Divide dough into 8 large portions (about 125 g each).

Flatten dough, place frozen Biscoff disc in the center, and wrap dough completely around it, sealing well.

Shape into tall domes and place in an airtight container.

Refrigerate for at least 12 hours (minimum 2 hours).

Preheat oven to 180°C (350°F).

Place chilled cookies on a lined baking tray, spaced well apart.

Bake for 18–19 minutes until edges are golden and centers are just set.

Press extra white chocolate chips on top while hot if desired.

Cool on the tray for 20 minutes before serving.