• Make the Dough
• In a large mixer, beat the butter and both sugars together then add the egg, milk, and vanilla, blending on medium-high speed for about 20-30 seconds.
• Add the flour, baking powder, and salt, mixing for another 20-30 seconds beat until a dough forms.
• Divide the dough into thirds, form it into a ball with your hands and then wrap each with plastic wrap, chilling in the refrigerator at least 4 hours or 8 hours/overnight.

Form and Bake the Hamantaschen

• Preheat the oven to 375 F.
• Roll out one piece of dough on a floured surface so it's about ⅛-inch thick. Use the rim of a juice/rocks glass to cut out 3-inch circles. Repeat with the remaining dough; you may need to form it into a ball again and then roll it out to use as much dough as possible.
• Spoon a teaspoon of jam into the center of each dough circle.
• With your fingers, gently fold the edges of each dough circle to form a triangle, pinching each one at three corners to keep the filling in but leaving the center slightly exposed.
• Arrange the cookies on 2 large baking sheets and bake them for 8-10 minutes until the stat to lightly brown.
• Cool them on a baking sheet for a couple minutes before moving them to a wire rack to cool completely. Store them in an airtight container for up to 5 days.