Beat the 1 cup (225g) softened butter, 1 cup (200g) granulated sugar, and 1/2 cup (110g) brown sugar together on medium speed for 3 minutes until pale and fluffy.

Add the 2 eggs one at a time, then mix in the 1 tsp vanilla extract and 3/4 cup (210g) Biscoff spread on medium speed for 60 seconds until smooth and glossy.

Whisk the 2 1/2 cups (315g) flour, 1 tsp baking soda, 1/2 tsp salt, and 1 tsp cinnamon together in a separate bowl, then fold into the wet ingredients until just combined.

Scoop the dough into 12 balls using a 1/4 cup measure, flatten each to 3/4 inch thick, and bake at 375°F (190°C) for 11 to 13 minutes until the edges are set and the centers look slightly underdone. Cool on the pan for 10 minutes, then transfer to a wire rack and cool completely.

Beat the 1/2 cup (115g) softened butter for 2 minutes, then add the 1 cup (130g) sifted powdered sugar, 1/2 cup (140g) Biscoff spread, 2 tbsp heavy cream, and a pinch of salt. Beat for 2 to 3 minutes until fluffy and glossy.

Swirl the frosting onto each cooled cookie with a spoon or small offset spatula, then press a piece of Biscoff cookie into the center of each one.