Preheat your oven to 350°F (180°C) with the rack in the middle position. Line a pan with parchment paper.

Line a small baking sheet or plate with wax paper. Drop the Nutella by 2-teaspoon dollops onto the wax paper. You need 10 dollops total. Put the whole thing in the freezer to harden while you make the dough.

Toast the walnuts in a dry frying pan over low heat until they smell nutty and fragrant. Let them cool completely, then chop into small pieces.

In your stand mixer with the paddle attachment, beat the butter, brown sugar, white sugar, and peanut butter together until smooth and combined.

Add the vanilla extract, salt, baking powder, baking soda, and nutmeg. Beat on medium speed until the mixture is light and fluffy, about 8 minutes (try not to speed run this!). Scrape down the sides of the bowl a few times as you go.

With the mixer running on low, add the eggs one at a time. Let each egg fully incorporate before adding the next.

Still on low speed, add the flour and toasted walnuts. Mix just until everything comes together into a soft dough.

Divide the dough into 10 equal portions — about 135 grams each if you’re weighing. Roll each portion into a ball, then flatten it into a disc with your palm.

Pull the frozen Nutella dollops out of the freezer. Place one dollop in the centre of each dough disc, then fold the edges up and around to completely seal the Nutella inside. Roll gently to smooth the seam.

Place 4 dough balls on your prepared baking sheet, spacing them well apart. Sprinkle with flaky salt if you like.

Bake for about 22 minutes, until the edges are golden and the tops look set. Let the cookies cool completely on the baking sheet before moving them — they’re fragile when warm.

Repeat with the remaining dough balls, baking in batches of 4.