Directions

1. In bowl of electric mixer fitted with the paddle attachment, cream butter and sugar until fluffy, about 4 minutes. Add eggs, one at a time, beating well after each. Sift flour, baking soda, and salt into large bowl. On low speed, gradually add flour mixture to mixer bowl, alternating with buttermilk, until combined. Wrap dough in plastic; chill until firm, 1 hour or overnight.
2. To color white sanding sugar, if using: Place a few tablespoons in a small bowl. Mix in petal dust with a toothpick, a bit at a time, until desired shade is reached. Colored sanding sugar will last indefinitely.
3. Heat oven with two racks centered to 350 degrees. Line 2 baking sheets with parchment paper. On lightly floured surface, roll chilled dough 1/8 inch thick. Cut out hearts using any 1- to 3 1/2-inch heart cookie cutters. If desired, cut centers out of some hearts. Transfer with spatula to baking sheets. Chill for 30 minutes. Sprinkle with sanding sugar, if using. Bake until just golden but not too brown, about 10 minutes. Transfer cookies to rack. Continue with dough; reroll scraps.
4. To make sandwich hearts: Brush bottom heart lightly with jam; cover with a second heart with center cut out; jam will adhere hearts. Fill cut-out area with more jam. Cookies will keep, in an airtight container, at room temperature for 1 week.