Use a medium-sized bowl to beat butter, cream cheese, milk and sugar with a stand or hand mixer. Mix until evenly blended. Then, beat in egg yolk.
Sift flour and baking powder, and then stir into mixture. Dough will be very stiff once all ingredients have been mixed. Cover bowl with plastic wrap and refrigerate overnight.
After refrigerating overnight, preheat oven to 400 degrees.
Use a floured surface to roll out dough. Once dough is approximately ¼ inch thick, begin cutting with a heart-shaped cookie cutter (the larger the cutter the smaller the total yield).
Place on an ungreased baking sheet and begin adding a spoonful of raspberry filling to each center. You can make thumbprint impressions in the center to allow filling to smoothly set, or create your own desired shape in the center.
Bake for 10-12 minutes, or until golden brown.
Cool completely and decorate further, if desired, with sprinkles, decorative sugar, chocolate or confectioners sugar.