In a small light colored saucepan over medium heat, melt the butter and cook it until it's deep golden and fragrant. When brown specks begin to appear, remove it from the heat and immediately transfer it to a small bowl. Cover and refrigerate the brown butter until firm, about 2-3 hours or overnight. When the butter has firmed up, cut it into cubes.

Preheat the oven to 375ºF (190ºC). Line a large baking sheet* with parchment paper.

In a large bowl, whisk together the flour, baking powder and salt. Whisk in the brown sugar.

Work the brown butter into the flour mixture with your fingertips or with a pastry blender until pea size pieces are formed.

In a small bowl, whisk together the heavy cream, sour cream, egg yolk and vanilla. Pure this mixture into the flour mixture. Stir just until a shaggy dough forms. Fold in the chocolate chips.

Turn the dough out onto a lightly floured surface. Fold the dough over onto itself a couple of times. Do not overwork the dough. Form the dough into a 7-inch wide, 1-inch thick round. Cut it into 8 wedges.

Place the scones onto the prepared baking sheet. Brush the tops of the scones with heavy cream and sprinkle with coarse sugar. Bake until the scones are golden brown, about 15-18 minutes. Serve warm.