Preheat your oven to 180 degrees Celsius.

In a suitable mixing bowl, combine the ground meat, egg, breadcrumbs, grated onion, minced garlic, baking soda, salt, and black pepper. Knead the mixture until well combined.

Tear off pieces of the meat mixture and shape them into small balls. Arrange the meatballs on a baking tray lined with parchment paper.

Bake the meatballs in the preheated oven for about 25-30 minutes, or until they are cooked through and slightly browned.

While the meatballs are baking, heat 5 tablespoons of oil in a suitable pan over medium heat.

Add the chopped onion and capia pepper, sautéing until the onions are translucent.

Add the chopped mushrooms to the pan along with any desired spices. Cook until the mushrooms release their liquid and begin to absorb it, about 5-7 minutes.

Stir in the tablespoon of starch and gradually add the milk, stirring continuously until the mixture comes to a boil and thickens.

Once the meatballs are done baking, remove them from the oven. Place the roasted mushrooms at the bottom of a serving dish, and then add the meatballs on top.

Top the meatballs with grated cheddar cheese and return to the oven. Bake until the cheese is melted and slightly browned, about 5-10 minutes.

Serve the dish hot for a delightful meal.