One-Pot Meatball Orzo & Broccoli Rabe Casserole

Ingredients

• 2 tablespoon olive oil, divided
• 1 tablespoon minced garlic
• 6 cup roughly chopped broccoli rabe
• 1 teaspoon hot pepper flakes
• kosher salt, to taste
• 1/2 cup chopped onion
• 16 ounce package of orzo
• 4 cup less-sodium chicken stock
• 26 ounce pkg. of frozen meatballs, such as rosina homestyle meatballs (or italian/turkey)
• 1/2 cup finely grated parmigiano-reggiano cheese, plus more for serving