Preheat then oven to 375° F and prepare a cookie sheet with parchment paper or a silicone mat.
Beat the butter and cream cheese with a paddle attachment until it's light and fluffy and completely combined then add in the flour.
Roll dough on a lightly floured surface to ⅛ inch thickness and cut 2.5 inch circles with a cookie cutter or a large cup. Place the cookies on the cookie sheet and add ¼ teaspoon of jam in the center of the circle. Wet a basting brush with some milk and paint on one the right side of cookie.
Fold the left side over first then the right side (with the milk) and press the dough down to stick.
Bake for 15 minutes.
Cool on a cooling rack and sprinkle with powdered sugar.