In a medium bowl, whisk together the flour, baking soda, baking powder, cornstarch and salt. Set aside.

In a microwave safe bowl, melt the butter. Then whisk the peanut butter into the hot, melted butter until well combined.

With a spatula or wooden spoon stir in the granulated sugar and brown sugar until well combined.

Add the eggs and yolk, one at a time, stirring well after each addition. Add in the vanilla.

Stir in the flour mixture. Fold in the peanut butter chips. Cover and refrigerate the dough for at least 2 hours, up to overnight.

Position a rack in the center of your oven and preheat the oven to 350ºF (180°C). Line baking sheets with parchment paper or silicone baking mats.

Using a medium cookie scoop, scoop the cookie dough into 2-tablespoon portions. Flatten the cookie dough and place jam in the middle, folding the cookie dough around it.

Bake for 10-12 minutes, or until golden brown. Remove from the oven and cool for 5 minutes before transferring to wire racks to cool completely.