Scrub and dry the sweet potatoes, then prick each with a fork. Microwave for 13 to 18 minutes until tender. Once cool enough, scoop out and mash 1 cup of the flesh.

Once the sweet potato is cool, mix in ricotta, Parmesan, egg, salt, and nutmeg. Add 3/4 cup flour and stir until combined. If sticky, add more flour gradually.

Dust a work surface with flour. Roll the dough into 4 ropes, each about 1/2 inch thick, and cut into 1-inch pieces. Dust with flour if needed.

Toast hazelnuts at 375°F for 5 to 9 minutes until fragrant. In a pan, melt butter over medium heat until it browns to a mahogany color. Add sage for about 30 seconds.

Drop gnocchi into boiling salted water. Boil until they float, then for 30 seconds more. Transfer directly into the sage brown butter and toss gently.

Store any leftover gnocchi in an airtight container in the fridge for up to 2 days, or freeze formed pieces on a floured baking sheet. Reheat gently.