Gnocchi with Sage, Butter, and Parmesan

INGREDIENTS

2 1/2 lb

russet potatoes (about 4 large), scrubbed

1 1/4 cups

all-purpose flour, plus more for dusting

2 tsp

kosher salt, plus more

egg, beaten to blend

4 tbsp

unsalted butter, cut into small pieces, room temperature

2 oz

Parmesan, finely grated, plus more for serving

sage leaves

Freshly ground black pepper