Step 1: Line a tray with parchment paper and scoop 12 individual teaspoons of Biscoff spread onto it. Place in the freezer for at least 60 minutes until rock hard.
Step 2: In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until pale and fluffy (about 3-4 minutes).
Step 3: Beat in the egg and vanilla extract until well combined.
Step 4: Sift in the flour, cornstarch, baking soda, and salt. Mix gently until just combined; do not overmix.
Step 5: Divide the dough into 12 equal portions (approx. 70-80g each).
Step 6: Take one portion of dough, flatten it, and place a frozen Biscoff disc in the center. Wrap the dough around it, ensuring it is fully sealed.
Step 7: Place the dough balls on a tray and chill in the fridge for 30 minutes. Preheat your oven to 350°F (175°C).
Step 8: Arrange the balls on a baking sheet spaced 3 inches apart and bake for 10-12 minutes until the edges are golden but the centers are still soft.
Step 9: Allow the cookies to cool on the baking sheet for 10 minutes before transferring to a wire rack.