Melt the butter until it's liquified but not hot. You may have to melt for 30-40 seconds and stir until it dissolves.
Add the granulated and brown sugar and stir until combined.
Stir in the peanut butter until smooth.
Add the egg and vanilla and stir to combine.
Fold in the flour, baking soda and salt. The dough should be cohesive and pull away from the sides of the bowl.
Scoop 3-tablespoon balls of dough onto parchment paper lined baking sheets, leaving about two inches of space between cookies.
Use a spoon or the bottom of a glass to press the cookies to about 1/2" thickness.
Spoon a heaping teaspoon of jam onto the top of each cookie making sure it doesn't run over the sides.
Bake at 350F for 10-11 minutes, or until the edges begin to brown.
Remove from the oven and allow to cool completely on the baking sheets.
Drizzle with melted peanut butter and coarsely chopped peanuts.
Notes
The importance of leaving cookies on the baking sheet: To prevent the cookies from getting too brown or dry, remove them when the edges are just starting to brown, leaving them slightly undercooked. Cooling them on the baking sheet will finish the baking process.
Fixing cookies that have spread: Place a round cookie cutter or small bowl over each cookie and, using a circular motion, gently swirl it around the edges of the cookies. This works best when the cookies are hot and fresh out of the oven.
Storage: Keep at room temperature for up to one week.