Peanut Butter and Jelly Cookie Cake

Whisk flour, baking soda, and salt in a medium bowl. Put butter, peanut butter, and sugars into mixer bowl; mix on medium-high until pale and fluffy. Mix in egg and yolk. Reduce speed to low. Add flour mixture; mix until just combined. Remove 2 1/2 cups dough. Divide it in half; shape into disks. Wrap each in plastic; refrigerate 30 minutes or overnight. Add molasses to remaining dough in mixer; mix on low speed until combined. Transfer to a pastry bag fitted with a 1/4-inch plain round tip (such as Ateco #7). Preheat oven to 350 degrees F. On lightly floured parchment, roll out 1 disk of dough to 1/4 inch thick. Transfer with parchment to baking sheet; freeze until firm, about 10 minutes. Repeat with remaining dough. Cut dough into 2 1/2-inch squares; space 1 inch apart on baking sheets lined with parchment. Pipe molasses dough around edges for "crust." Score diagonally. Freeze until firm, about 15 minutes. Bake until centers are pale golden, 6 to 8 minutes. Transfer to wire racks to cool. Carefully break each cookie at scoring. Spread 1 teaspoon jam on half of the cookies; sandwich with remaining cookies.