2 cups all-purpose flour
1/4 teaspoon salt
3/4 cup packed brown sugar
2/3 cup granulated sugar
1/2 cup chunky peanut butter
1/4 cup butter, softened
2 large eggs
1 teaspoon vanilla extract
1/2 cup Strawberry jam
Prepare cookie sheets with parchment paper or silpat.
In a medium bowl, combine flour with the salt and set aside.
In the work bowl of your stand mixer, cream together butter and sugar. Add peanut butter and combine well. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla. Gradually add flour mixture to sugar mixture, beating on low speed just until combined.
Lightly coat hands with cooking spray (important as the dough is pretty sticky!). Shape dough into 3-40 balls (about 2 1/2 teaspoons each). Place balls 2 inches apart on baking sheets lined with parchment paper. Press thumb or back of a wooden spoon into center of each dough ball, leaving an indentation. Cover and chill 1 hour.
Preheat oven to 350F.
Bake cookies for 8 minutes. Remove from oven and redefine thumbprints with the back of the wooden spoon as necessary. Return to oven and bake for an additional 6-8 minutes, until lightly browned. Cool on a wire rack completely. Spoon about 1/2 teaspoon preserves mixture into the center of each cookie. Let dry for a few hours uncovered before storing in an airtight container.