1 cup (2 sticks) unsalted butter, cut into tablespoon slices
2-1/2 cups bread flour
1/2 teaspoon coarse sea salt (I used fleur de sel but you can also use regular salt)
1 teaspoon baking soda
1/4 cup granulated sugar
1-1/4 cups light brown sugar
1 large egg
1 large egg yolk
2 tablespoons milk
1-1/2 teaspoons vanilla extract
2 cups milk chocolate chunks
1. In a small pot melt the butter over medium heat, whisking occasionally. Once melted, the butter will foam up, and then subside. Continue cooking, stirring occasionally, until light brown specks form at the bottom of the pot and the butter has a nutty aroma. Careful not to let it burn. Remove from heat and pour into a glass bowl. Set aside to cool.
2. In a small bowl, sift together the bread flour, salt and baking soda. Set aside.
3. In a small bowl whisk together the milk, egg, egg yolk and vanilla extract, and set aside.
4. Using an electric mixer with the paddle attachment, on medium speed cream together the cooled browned butter and sugars for 2 minutes.
5. On low speed, add in the egg mixture, mixing until well combined, about 30 seconds.
6. Slowly stir in the flour mixture, mixing until well combined, scraping down the sides as needed.
7. Stir in the chocolate chunks. Form into dough balls, dropping a spoonful of Nutella in the middle and wrapping the dough around to cover the filling completely. Alternatively you can drop a spoonful of dough in a ramekin, drop a dollop of Nutella over it then cover with another spoonful of dough, filling the ramekin 2/3 full.
8. Chill the dough balls (or ramekins) in the fridge overnight or up to 48 hours.
9. Preheat oven to 375 degrees F.
10. Line two cookie sheets parchment paper.
11. Place dough balls about 2 inches apart on each pan. Flatten balls slightly. If using ramekins, place on unlined baking sheet.
12. Bake for 10-12 minutes, rotating the pans half way through for evening browning.
13. Cool slightly before moving to a wire rack to cool completely. Serve warm.