Prep your pan and oven. Heat the oven to 400°F (200°C). Line a baking sheet with foil and set a wire rack on top, or just use the sheet. Lightly oil it to prevent sticking.

Make a quick panade. In a large bowl, combine 1/2 cup breadcrumbs and 1/3 cup milk. Let it sit for 2–3 minutes to soften. This mixture keeps the meatballs moist.

Build the meatball mix. Add 1.5 pounds ground turkey, 1 grated small onion (squeeze out excess liquid if very watery), 2 minced garlic cloves, 1 egg, 1/3 cup grated Parmesan, 2 tablespoons chopped parsley, 1 teaspoon kosher salt, 1/2 teaspoon black pepper, and a pinch of red pepper flakes. Mix gently with your hands until just combined.

Shape the meatballs. Lightly oil your hands and form golf ball–sized meatballs (about 1.5 inches). You should get around 18–20.

Brown for flavor. Heat 2 tablespoons olive oil in a large skillet over medium-high. Brown the meatballs in batches for 2–3 minutes per side until golden. Don’t cook through yet. Transfer to a plate. If you prefer, you can skip the skillet and bake them 12–15 minutes, but browning adds more taste.

Simmer in sauce. Pour your marinara into the same skillet (drain excess fat first) and bring to a gentle simmer. Nestle in the meatballs, reduce heat to low, cover, and cook 10–12 minutes, turning once, until cooked through. Internal temperature should hit 165°F (74°C).

Toast the rolls. Split the sub rolls and brush with a little melted butter or olive oil. Place on a sheet and toast in the oven for 3–4 minutes until lightly crisp at the edges. This helps the bread hold up to the sauce.

Assemble the subs. Spoon a little sauce onto each roll, add 3–4 meatballs per roll, top with more sauce, and lay on slices of provolone or mozzarella. Return the subs to the oven and bake 3–5 minutes until the cheese melts. For extra color, switch to broil for 1 minute, watching closely.

Finish and serve. Top with more Parmesan and chopped basil if you like. Serve hot with a side salad, roasted veggies, or chips.