1. Slice the onion and sauté it over medium heat in a saucepan with a drizzle of olive oil. When the onion becomes translucent, add the ground meat and cook for 5 minutes, stirring occasionally. Then pour in the tomato sauce, water, and peas. Season with salt, pepper, sprinkle with basil and bicarbonate*. Mix well and let it simmer over medium heat for at least one hour.
2. Preheat the oven to 230 degrees Celsius.
3. Cook the tortellini until "al dente". Drain them. In a large bowl, combine the tortellini with 2/3 of the bolognese sauce. Add the grated cheese and mix well. Transfer everything to a gratin dish.
4. Pour the remaining bolognese sauce on top. Add diced mozzarella and bake for 15-20 minutes until it is golden and bubbly.
5. Serve hot straight from the oven.
6. Enjoy!