Preheat the oven to 180ºC or 350ºF.
Heat the olive oil in the pan and place it over medium heat. Once the oil is hot, add in the slices of chorizo. Once the chorizo slices are crispy, remove them to a plate and set aside. Pour out all but 1 tablespoon of the chorizo fat.
To the remaining chorizo fat, add the diced onion and the minced garlic. Cook over medium heat until the onions are soft, fragrant and just starting to turn golden.
Add the tomato and red pepper sauce to the pan and stir into the onions and garlic really well. Make the chicken stock using the stock cube and dissolving in boiling water. Pour the stock into the pan and stir well. Bring to a gentle simmer for about 5 minutes until the sauce and stock are well incorporated.
Stir the spinach into the stock and remove the pan from the heat. The spinach will wilt naturally in the heat of the sauce. Add in the gnocchi and stir everything really well so that the gnocchi are well coated in sauce.
Add the chorizo back into the pan and mix it into the sauce and stir in the lemon zest and chopped basil. Tear the mozzarella into large chunks and place it on top of the gnocchi. Bake in the preheated oven for about 20 minutes, or until the mozzarella is golden, bubbling and melted.