Prep the broccoli rabe. Trim off tough stem ends and cut the rest into 1–2 inch pieces. Rinse well to remove grit.

Blanch to tame bitterness. Bring a large pot of salted water to a boil. Add broccoli rabe and cook for 2–3 minutes, until bright green and slightly tender. Drain and immediately plunge into ice water. Squeeze out excess moisture and chop finely.

Sauté the aromatics. Heat 1 tablespoon olive oil in a skillet over medium. Add garlic and red pepper flakes. Cook 30–60 seconds until fragrant, not browned.

Cook the sausage. Add sausage to the skillet, breaking it up. Cook until browned and no longer pink, 6–8 minutes. Drain excess fat if needed.

Combine with greens. Add chopped broccoli rabe to the skillet and toss with sausage for 2 minutes. Season with a pinch of salt, black pepper, and lemon zest. Let cool slightly.

Make the mixture. In a bowl, mix the sausage-greens mixture with Parmesan, breadcrumbs, and egg until cohesive. It should be moist but hold its shape. If too wet, add more breadcrumbs by the tablespoon.

Form the bites. Roll into 1–1.5 inch balls. If using mozzarella, press a small cube into the center and seal it inside.

Choose your finish: bake or pan-sear. Bake: Heat oven to 400°F (200°C). Place bites on a parchment-lined sheet, brush with remaining olive oil, and bake 12–15 minutes until browned and set.

Pan-sear: Heat 2 tablespoons oil in a nonstick skillet over medium. Cook bites, turning, until browned on all sides and heated through, 8–10 minutes.

Serve. Sprinkle with extra Parmesan and a squeeze of lemon. Serve on crostini or with toothpicks and a simple mustard or marinara on the side.