Sweet Potato Gnocchi with Fried Sage and Shaved Chestnuts

INGREDIENTS

1 1/4

lbs Russet (baking potatoes)

1 cup

Sage

1 3/4 lb

Sweet potato

Egg, large

1 1/2 cups

All-purpose flour plus more

1/2 tsp

Nutmeg, grated

1/3 cup

Olive oil, extra-virgin

1/3 cup

Chestnuts, bottled roasted

2 tbsp

Butter, unsalted

1/3 cup

Parmigiano-reggiano plus more