Heat olive oil in a large oven-safe skillet over medium heat.
Add the sliced chorizo and sauté for 4-5 minutes until the fat renders and the sausage starts to brown.
Add the diced onion to the skillet and cook for 3-4 minutes until softened.
Stir in the minced garlic and cook for 60 seconds until fragrant.
Pour in the crushed tomatoes and dried oregano. Season with salt and pepper, then simmer the sauce for 5-7 minutes.
While the sauce simmers, cook the gnocchi in a large pot of boiling salted water until they float to the surface (approximately 2 minutes). Drain well.
Gently fold the cooked gnocchi into the chorizo tomato sauce until evenly coated.
Scatter the mozzarella pieces over the top of the skillet.
Place the skillet under a preheated broiler for 2-3 minutes until the mozzarella is melted, bubbly, and slightly golden.
Garnish with fresh basil leaves and serve immediately.