Line a small baking sheet with parchment paper. Dollop 12 individual teaspoons of creamy peanut butter on the tray. Place in freezer to firm up.
Preheat oven to 350 degrees. Line another large baking sheet with parchment paper. Set aside.
In a medium bowl, whisk together flour, cocoa powder, espresso powder, baking soda and salt. Set aside.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in the egg and vanilla. Add the dry ingredients to the wet until well combined.
Roll heaping tablespoonfuls of dough around dollops of frozen peanut butter, sealing to completely cover. Place two inches apart on prepared sheet. Sprinkle with Maldon sea salt flakes. Bake for 9-10 minutes. Do not over bake, Cool on sheet for 5 minutes before removing to wire rack to cool completely.