
Start by placing the ground beef inside the large onions with their cores removed.
Next, shape the meat inside all the onions by making a hole in the center.
Place one cube of cheddar cheese in each one.
Then, transfer them all to a large skillet over medium to low heat with boiling water.
Cover the skillet and let them cook for 10 minutes.
After this time has passed, remove them from the hot water and set aside.
In a large bowl, add the finely diced tomatoes, the grated mozzarella cheese, the mushrooms cut into smaller pieces and the mayonnaise.
Season with the salt, the black pepper and mix everything very well until combined.
In a large baking tray add the medium potatoes cut into thin slices covering the entire bottom.
Season with salt and black pepper to taste.
Add the mixture we prepared and spread it over the potatoes.
Next, add the onions we prepared earlier add one egg yolk on top of each onion.
Season with salt and black pepper to taste.
Add the grated mozzarella cheese, dividing it on top of each egg yolks
Place in a preheated oven at 180° C (350° F) and bake for 35 minutes.
Serve.