Brown 11 tbsp butter in skillet over medium-high until deep golden, 3-5 min.

Pour into bowl, stir in remaining 4 tbsp butter until melted. Cool 15 min.

Heat oven to 350F. Line two baking sheets with parchment.

Mix granulated sugar with 1/4 cup brown sugar in shallow bowl for coating.

Whisk flour, baking soda, and baking powder in separate bowl.

Mix remaining brown sugar and salt into cooled butter.

Add egg, yolk, and vanilla. Mix until blended.

Stir in flour mixture until combined.

Roll dough into 24 balls (2 tbsp each).

Coat balls in sugar mixture.

Place 12 per sheet, 2 inches apart.

Bake one sheet at a time 12-14 min until edges set but centers soft.

Let rest on sheet 5 min.

Transfer to rack and cool completely.