Heat the oven to 200 C / 400 F. Warm 1 tbsp olive oil in a 26 cm / 10-inch skillet over medium heat, add the garlic and cook for 30 seconds until fragrant. Add the spinach in three handfuls, stirring until each wilts, about 3 to 4 minutes total.

Tip the spinach onto a plate and cool for 5 minutes. Wrap it in a clean kitchen towel and twist hard until almost no liquid comes out, then chop it fine. Stir it into the ricotta with the parmesan, lemon zest, nutmeg, 1/4 tsp salt and 1/4 tsp pepper.

Cut a pocket into the thick side of each breast, about 7 cm / 3 inches deep, stopping before the knife reaches the other edges. Spoon about 4 tablespoons of filling into each pocket and close with toothpicks. Rub the breasts with 1 tbsp olive oil, 3/4 tsp salt, 1/2 tsp pepper, the Italian seasoning and the garlic powder.

Spread the marinara in a 23 x 33 cm / 9 x 13-inch baking dish. Set the breasts on top with the pocket side facing up, spaced a little apart.

Bake for 27 minutes, then scatter the mozzarella over the breasts and bake 5 minutes more, until the cheese melts and an instant-read thermometer reads 165 F / 74 C in the thickest part of the meat.

Rest the chicken in the dish for 5 minutes. Remove the toothpicks, spoon sauce from the dish over each breast and top with torn basil.