Preheat your oven to 350°F (175°C).

Cream together the softened butter, granulated sugar, and brown sugar until smooth.

Beat in the eggs, one at a time, and stir in the vanilla extract.

In another bowl, combine the flour, baking powder, and salt, then gradually add this mixture to the creamed mixture.

Roll out the dough and cut it into rectangles.

Place a small spoonful of fruit jam on half of the rectangles and top with another rectangle. Seal the edges.

Bake in the oven for 10-12 minutes, until lightly golden.

Let cool, then mix powdered sugar with milk to make the icing. Drizzle over the cookies and add sprinkles if desired.