Broccoli Rabe Penne with Broccoli Rabe and Sausage

Ingredients

• 1 pound penne pasta
• 1/4 cup olive oil
• 3 large cloves garlic, crushed
• 1 1/2 pounds broccoli rabe, florets and tender leaves and stems only
• 1/4 teaspoon red pepper flakes, crushed
• 1/4 teaspoon salt
• 1 cup chicken stock or canned broth
• 1/2 pound Italian sausage (sweet or hot) cooked and crumbled/chopped
• 2 teaspoons unsalted butter
• 1/2 cup parmigiano-reggiano cheese, freshly grated