►Combine squash, ricotta, Parmigiano Reggiano, egg, salt and nutmeg in a large bowl. Fold in flour a little at a time until dough is slightly stiff, but still sticky.
► Divide dough into eight equal pieces on a lightly floured surface. Roll each piece into a long rope, about an inch in diameter. Using a knife or bench scraper, cut each rope into 3/4-inch pieces. Transfer to baking sheet.
►Bring a large pot of salted water to a boil. Working in batches, cook gnocchi until tender, stirring occasionally, about 5 minutes. Use a slotted spoon to transfer cooked gnocchi to a clean baking sheet to cool.
►Fry pancetta in a large skillet over medium-high heat until crisp and brown, about five minutes. Using a slotted spoon, remove pancetta but reserve rendered fat. Set aside.
►Add gnocchi to pan and cook until golden brown, flipping once, about 2-3 minutes per side. Stir in spinach until just wilted. Remove from heat.
►Melt butter in a small saucepan. Stir in Stilton until combined. Add mixture to gnocchi and toss gently to coat gnocchi with sauce. Serve warm with crispy pancetta on top.