Preheat oven to 350F.
Place meat in a mixing bowl. On a cutting board, combine zest with parsley and 2 cloves of garlic and finely chop together to make a gremolata. Add gremolata and breadcrumbs to the meat along with egg, milk, salt, pepper, 1/4 to 1/3 cup grated cheese and about 2 tablespoons EVOO. Combine meatballs and roll into walnut-sized balls. Arrange on a nonstick baking sheet and roast 15 minutes or until cooked through.
Place a large pot of water on stove to boil for spaghetti.
Simmer peas in stock, covered; 5 minutes if raw, 2 minutes if frozen. Remove from heat. Add 1 cup peas to a food processor. Once peas are cooled to room temperature, add remaining clove of garlic, basil, mint, salt, pepper, 1/4 to 1/3 cup EVOO, and cheese. Process into a pesto sauce.
Return peas and stock to heat, bring to a low simmer and stir in crme fraiche. Keep warm over low heat and let thicken.
Cook spaghetti in salted boiling water to al dente. Remove 1/2 cup of starchy cooking water then drain pasta.
Stir pesto into creamy peas and combine with pasta and meatballs.