Kosher salt
1/2 lb. fusilli or other twisted pasta
4 oz. pancetta, sliced 1/4 inch thick and cut into 1/2 -inch squares (3/4 cup)
1 large clove garlic, smashed and peeled
1/2 lb. green beans, trimmed and cut into 1-inch lengths (2 cups)
Freshly ground black pepper
2 Tbs. unsalted butter, at room temperature
2 oz. finely grated Parmigiano-Reggiano (1 cup)