Preheat oven to 375 F. In a large frying pan, heat olive oil over med-high heat. Add onions and garlic, sauteeing for 30 seconds until fragrant. Add ground beef. Cook, breaking up with a spoon. Add mushrooms and cook another 2 min. Add both jars of passata to ground beef mixture, along with salt and pepper. Simmer for 15 minutes.
Meanwhile cook quinoa according to package directions and prepare peppers by slicing length-wise in half and removing core/seeds. Drizzle with a tiny bit of olive oil and bake, covered in foil, in a large oven safe dish for 15 minutes.
Add cooked quinoa to ground beef and tomato mixture, along with kale. Stir well and remove from heat.
Remove peppers from the oven and when cool, add 2-3 tbsp of ricotta to each pepper, just enough to coat the bottom of each. This should use up the whole tub.
Add quinoa-ground beef mixture to each pepper - continue until mixture is used up. Peppers will be heaping full of stuffing. Bake, covered with foil, in oven for another 15 minutes.
Remove from oven, top with grated mozzarella, and bake uncovered another 5 minutes or until cheese is melted. Remove from oven, sprinkled with fresh chopped basil and serve!