Pumpkin Tortelli with Brown Butter and Sage

1 sugar pie pumpkin or butternut squash, about 1 1/2 lb.  

1 egg yolk 

1/4 cup grated Parmigiano-Reggiano cheese 

Sea salt and freshly ground pepper, to taste 

Pinch of freshly grated nutmeg 

Flour for dusting 

1 lb. fresh egg pasta dough

2 Tbs. salt 

8 Tbs. (1 stick) unsalted butter 

About 10 small fresh sage leaves