Preheat the grill to medium. Put the peppers on a large baking tray, cut-side up, and grill for 5-10 minutes until softened.
Meanwhile, in a large pan, heat the oil over a medium heat. Add the onion and the Mexican spice blend and cook for 5 minutes. Add the mince and mushrooms and cook for a further 5 minutes, until browned. Stir through the rice and half the cherry tomatoes and gently cook for 1-2 minutes.
Spoon the mixture into the peppers, then top with the remaining cherry tomatoes and the goat's cheese. Grill for 10 minutes until golden and the cheese is soft. Serve with the mini cornbread.