Preheat the oven to 400°F (200°C).

Place the chicken breasts on a baking sheet lined with parchment paper. Cut 5 slits into each breast, being careful not to cut all the way through. Brush a little mustard over the chicken. Insert a piece of mozzarella and a slice of chorizo into each slit.

Season with salt and pepper to taste, and sprinkle with your choice of herbs. Place a sprig of rosemary on top of the chicken and bake for 15 to 20 minutes.

Serve the chicken with sautéed vegetables, pasta, rice, or ratatouille.

Variation: For a lighter version, replace the chorizo slices with tomato slices, add a few basil leaves, and use tomato sauce instead of mustard.