Preheat oven to 375 degrees and line baking sheets with parchment
In medium bowl, sift or whisk flour, cocoa powder, baking soda and salt
In another bowl or mixer, beat butter, peanut butter, 3/4 cup of granulated sugar and all light brown sugar until smooth.
Add egg and vanilla and mix until blended. Gradually add flour and mix until just incorporated. Don't continue to mix once you can't see flour.
In a small bowl place the remaining 1/4 cup of granulated sugar. Form dough into 1/4 cup balls and roll in the sugar. Should make about 10 balls. Only place 5 balls on a baking sheet and make sure they have space between them.
Use a 1/4 tsp to make an indentation in center of each ball (1/2 to 3/4 inch deep). Spoon a tsp of jam into each indentation
Bake cookies for 11-14 minutes until cookies are crackled and dough has spread. Cool for 5 minutes before transferring to rack and then cool completely for 20 minutes before eating.