Freeze Biscoff Pucks
Line a plate or small tray with parchment paper. Dollop the Biscoff spread into 8 equal discs (roughly 1/2 inch thick). Freeze for 1 hour or until firm enough to handle.

Brown the Butter
Place the cubed butter in a light-colored saucepan over medium-high heat. Melt and simmer for 4–5 minutes, stirring occasionally. Watch closely: Wait for the butter to foam up and for golden brown specks to appear at the bottom. It should smell nutty and toffee-like.

Cool Butter
Immediately pour the browned butter (scraping all the tasty brown specks) into a large heatproof bowl. Let it cool to room temperature (about 45 minutes). It must be cool so it doesn’t melt the chocolate chips later.

Mix Dry Ingredients
In a medium bowl, whisk together the flour, cornstarch, baking powder, baking soda, salt, cinnamon, allspice, and ginger.

Mix Wet Ingredients
Add both sugars to the cooled butter and mix with a wooden spoon. Stir in the egg, egg yolk, and vanilla until smooth and glossy (texture should resemble caramel).

Combine
Add the dry ingredients to the wet mixture and mix until just barely combined. Fold in the white chocolate chips.

Stuff the Cookies
Divide the dough into 8 portions (approx. 125g each). Technique: Flatten a portion of dough, place a frozen Biscoff disc in the center, and wrap the dough around it. Shape into a tall ball/dome, sealing cracks carefully to prevent leaks.

Chill (Crucial Step)
Place the dough balls in an airtight container and refrigerate for 12 to 24 hours. Note: Minimum chill time is 2 hours, but longer is better for flavor and texture.

Bake
Preheat oven to 350°F (180°C). Place cold dough balls 3 inches apart on parchment-lined baking sheets (bake 4 per tray). Bake for 18–19 minutes until edges are golden and the surface looks set but still pale.

Cool
Press extra chocolate chips on top immediately while hot. Let cool on the tray for 20 minutes to firm up, then transfer to a wire rack.