1 large egg
1 1/3 cups all-purpose flour, plus more for dusting
½ teaspoon baking soda
Pinch of salt
1/8 cup buttermilk
2/3 cup apricot or strawberry jam
1/4 cup powdered sugar for dusting, if desired
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar until fluffy, about 4 minutes. Add egg and continue beating until combined. Whisk flour, baking soda, and salt in a large bowl.
On low speed, gradually add the flour mixture to the mixer bowl, alternating with buttermilk, until combined.
Wrap dough in plastic; chill until firm, for one hour or overnight.
Preheat oven to 350 degrees F. Line a baking sheet with parchment paper. On a floured surface, roll chilled dough until it is about 1/8 inch thick.
For this step, you will need one large and one smaller heart-shaped cookie cutter. Cut out the large heart, then cut the centers out of half of the large hearts. Transfer to a baking sheet. Bake until lightly golden, about 9-10 minutes. Transfer cookies to rack. Continue with dough; re-rolling scraps and making more cookies until dough is used up.
To make heart cookies: Place jam on the bottom heart; cover with a second heart with center cut out. Jam will serve to bind the two heart shapes.
Dust the cookies lightly with powdered sugar for additional sweetness, if desired.