How to Prepare Appetizing Meatballs with Mushroom Sauce

Meatballs with Mushroom Sauce.

You can have Meatballs with Mushroom Sauce using 12 ingredients and 5 steps. Here is how you cook it.

It's 250 gr of grounded beef.
Prepare 1/2 cup of breadcrumbs.
You need 1 of egg.
You need 1 tbsp of homemade mild rub -- https://cookpad.com/us/recipes/2667371-mild-homemade-rub.
Prepare 50 gr of mozzarella, cubed.
You need 2 tbsp of oil.
It's 2 tbsp of flour.
It's 1 tbsp of butter.
Prepare 1 cup of broth.
You need 1/2 of onion, sliced thinly.
You need 125 gr of button mushrooms (champignon), sliced.
You need 1 tbsp of chopped celery.

Mix ground beef, breadcrumbs, egg, and homemade mild rub. Knead a bit. Form a ball and insert mozzarella inside. Seal it. Do it with the remaining of the mixture. I'd like to store them in the fridge for about 15 minutes, but you can skip this part if you're in a hurry..
Heat oil in a pan (medium). Add the meatballs and flip them around occasionally until the surface is brown. Remove them from pan and set aside..
Lower the heat. Add butter to the pan, then flour. Mix until it becomes a roux, adding broth bit by bit until you get a thick mixture..
Add the onion. When the onion has become a bit translucent, add mushrooms, then celery..
Add the meatballs to the pan and cover for five minutes or so..