Slice the onion, potato, mushrooms, and broccoli into appropriate sizes. Halve the cherry tomatoes and slice the Vienna sausages.

Whisk the eggs in a bowl, add milk, and mix well.

Heat a pan with oil over low heat and add the sliced potatoes. Cook until partially softened.

Add the onion, mushrooms, and broccoli to the pan and sauté together.

Season with salt and pepper, then add the sausages and cherry tomatoes. Continue cooking until all ingredients are well combined and cooked through.

Pour the egg mixture into the pan, gently stir the bottom with a spatula, and sprinkle mozzarella cheese on top.

Cover the pan with a lid and cook until the cheese melts and the eggs are set.

Use a spatula to gently move any uncooked egg from the top to the bottom of the pan. Cover again and cook until fully set.