In a large mixing bowl, beat the softened butter, brown sugar, and granulated sugar with an electric hand mixer until light and creamy.

Add the egg yolks and vanilla extract.

Beat until the mixture is smooth, pale, and fluffy.

In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and salt.

Gradually add the dry ingredients to the wet mixture.

Mix until a soft chocolate cookie dough forms with no dry flour remaining.

Fold in the chopped Ferrero Rocher chocolates using a rubber spatula until evenly distributed throughout the dough.

Scoop portions of the cookie dough and flatten each slightly in the palm of your hand.

Place a frozen Nutella portion in the center of each dough round.

Wrap the dough around the Nutella, sealing the edges completely, and roll into a smooth ball.

Arrange the filled cookie dough balls on a parchment-lined baking sheet, leaving about 2 inches of space between each cookie.

Bake in a preheated 350°F (175°C) oven for 10–11 minutes, or until the edges are set.

Remove the cookies from the oven and let them cool on the baking sheet for 10 minutes before transferring them to a wire rack to cool completely.

Serve and enjoy.