Line a small plate or tray with parchment paper. Using a small cookie scoop or spoon, scoop out 8 tablespoons (120 g) of Biscoff spread. Place the scoops on the tray and put it in the freezer for 20–30 minutes. This helps the filling stay firm while baking and keeps the cookies gooey inside. Set your oven to 400°F (205°C). Line two large baking sheets with parchment paper and set aside.
In a stand mixer fitted with the paddle attachment (or using a hand mixer), beat together the cold cubed butter (113 g), ¼ cup (65 g) Biscoff spread, white sugar, and light brown sugar. Beat on medium-high speed for about 3–4 minutes until the mixture looks pale, creamy, and fluffy.
Crack in the eggs one at a time, mixing well after each addition. Use a spatula to scrape down the sides and bottom of the bowl to make sure everything is evenly mixed.
Add in the flour, baking soda, baking powder, cornstarch, salt, cinnamon, and nutmeg. Mix on low speed until just combined. Do not overmix—stop as soon as you no longer see streaks of flour.
Gently fold in the white chocolate chips, semisweet chocolate chips, and crushed Biscoff cookies. The dough will be thick and packed with mix-ins—that’s what makes the cookies extra chunky and bakery-style.
Divide the dough into 8 equal portions (large cookie dough balls). Use your thumb to press a deep well into the center of each dough ball. Take one frozen Biscoff scoop from the freezer and place it inside. Carefully mold the dough around the filling so the Biscoff spread is completely covered.
Optional: Add 1 extra teaspoon of Biscoff spread on top of each dough ball for a crackled gooey topping.
Place 4 cookies on each baking sheet (they spread a little while baking). Bake one sheet at a time for 11–13 minutes until the edges are lightly golden but the centers still look slightly underbaked.
Remove from the oven and let the cookies cool on the baking sheet for at least 15 minutes before serving. This resting time allows the centers to set while staying soft and gooey inside.