1. Preheat the oven to 350°F. Butter a mini cheesecake pan.

2. Sift the flour, baking powder, and salt together in a medium bowl; set aside.

3. In a large bowl, cream the butter and sugar for 4 to 5 minutes. Add the milk and vanilla extract. Beat in the eggs one at a time, mixing well after each addition.

4. Using a rubber spatula, fold the flour mixture into the wet mixture until just incorporated; avoid overstirring.

5. Fill the mini cheesecake pan cavities halfway with batter. Bake 12 to 15 minutes, until a toothpick inserted into the center comes out clean or the top springs back when lightly pressed.

6. Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

7. For the buttercream filling, beat the butter, powdered sugar, and milk together until smooth, adding a little more milk as needed. Transfer to a piping bag if desired.

8. Slice the cooled cakes in half. Spread or pipe buttercream onto the bottom half of each cake, spoon jam over the buttercream, then top with the other cake half.

9. Dust the tops with powdered sugar before serving.