Veal and Sage Meatballs and Pasta with Gorgonzola-Walnut Sauce

Salt

1 egg

2 cloves garlic, thinly chopped

1 pound ground veal

6 to 8 sage leaves, thinly chopped, a few tablespoons

1/2 cup bread crumbs, a few handfuls

1/3 cup shredded Parmigiano-Reggiano

1/4 teaspoon freshly shredded nutmeg, watch it

Ground black pepper

Extra-virgin olive oil, for showering

3/4 cup chopped walnuts, separated

2 tablespoons all-purpose flour

2 tablespoons butter

1/2 cup dry white wine

1 cup cream

1 cup Gorgonzola, crumbled

1 cup chicken stock

3 to 4 cups (1 bunch) arugula or baby spinach, dirt free and trimmed