Preparation Steps

• Position a rack in the center of the oven and heat to 325°F (165°C). Line two sheet pans with parchment paper.
• Place the finely chopped peanuts in a shallow bowl. If your peanuts aren’t freshly roasted, toast them in a dry skillet over medium heat for 2–3 minutes until fragrant, then cool completely before using.
• In a medium bowl, whisk together the flour, baking soda, and fine sea salt.
• In a large bowl with a hand mixer (or stand mixer), beat the softened butter, peanut butter, and brown sugar on medium-high until light and creamy, about 2 minutes. Beat in the vanilla and egg just until smooth, about 30 seconds.
• Add the dry ingredients to the bowl and mix on low until a soft dough forms and no dry spots remain. Chill the dough for 15 minutes to firm slightly for easier rolling.
• Scoop dough into 1-tablespoon portions (about 20 g), roll into smooth balls, then coat each one in the chopped peanuts. Arrange on the prepared sheets, spacing about 2 inches apart.
• Use a 1/2-teaspoon measuring spoon to press a deep dimple into the center of each ball before baking. Bake 12–14 minutes, rotating the pans halfway, until the edges look set and the bottoms are pale golden.
• Immediately after baking, re-press the centers to reinforce the wells. Cool on the sheet for 5 minutes, then transfer to a rack to cool completely.
• Make the ganache: Warm the cream and espresso powder in a small saucepan over low heat until steaming (do not boil). Pour over the chocolate chips in a heatproof bowl. Let stand 2 minutes, then stir until smooth and glossy. Let thicken at room temperature for 10–15 minutes to a spoonable consistency.
• Fill and finish: Spoon or pipe the ganache into the centers of the cooled cookies. Sprinkle each with a tiny pinch of flaky sea salt, if using. Let stand until set, about 30 minutes.