Preheat your oven to 350°F (175°C).

In a large bowl, whisk together flour, sugar, baking powder, and salt until well mixed.

Cut in the cold butter using a pastry cutter until it resembles coarse crumbs.

Add eggs one at a time while mixing until combined.

Turn the dough onto a lightly floured surface.

Knead gently just until it holds together.

Roll out half of the dough to about 1/8-inch thickness.

Cut into rectangles using a sharp knife or pastry cutter.

Place filling in the center of half of them.

Place remaining rectangles on top of filled ones.

Press edges with a fork to seal tightly.

Bake for 15-20 minutes until golden brown.

Let them cool completely before icing.

Mix icing sugar with milk until smooth then drizzle over cooled cookies and add sprinkles if desired.