Line a plate or small cookie sheet with wax or parchment paper. Scoop ½ tablespoon sized balls of Nutella (about 24 of them) and place on cookie sheet. Freeze while preparing cookie dough.

Preheat oven to 350°F. Line two cookie sheets with silicone baking mats or parchment paper.

Mix butter and peanut butter in a large bowl with a hand mixer (or the bowl of a stand mixer fitted with the paddle attachment) until smooth. Add both sugars and cream until fluffy.

Add vanilla, egg, milk, baking soda and salt and mix until smooth, then add flour and mix just until cookie dough forms.

Place additional granulated sugar in a small bowl. Scoop 2-tablespoon sized cookie dough balls. Flatten ball of dough and place one small ball of frozen Nutella in the center. Fold the dough around the Nutella and roll to seal, then roll the cookies in sugar and place 2-inches apart on prepared cookie sheets. Use a fork to press the cookies and add the crisscross pattern.

Bake for 10-12 minutes, until they just lose their glossy sheen and the bottoms are lightly golden.

Cool on cookie sheets before removing and baking additional cookies.

Store in an airtight container for up to 3 days or freeze for up to a month.