In a large skillet pan add a generous drizzle of extra virgin olive oil and add finely chopped onion.Simmer for a few minutes on medium heat.
Extra virgin olive oil, 1 small onion
Add tomato puree + ½ cup water to thin out the sauce. Add an extra ¼ cups water if you're using hard Mozzarela cheese (see notes).Simmer for about 5 minutes on low heat.
2-2½ cups tomato sauce
Add salt and and just a few basil leaves. You should still have some left to add later.
Handful fresh basil leaves
Prepare Chicken Breast
Cut chicken breast in large cubes.
25 ounces chicken breast
Place chicken cubes in a big bowl and toss with flour.Mix well, making sure all chicken cubes are well dredged with flour.
⅓ cup flour
In a large skillet pan heat olive oil. Once oil is hot (but not burning!) add chicken cube shaking off excess flour.
Extra virgin olive oil
Add salt.
Salt
Once nice and brown on one side flip them with a spatula to get an even golden color on each side.
Mix Everything Together
Once chicken is all browned, add previously cooked tomato sauce. Mix well.
Top with fresh Mozzarella cut in cubes and a few basil leaves.Turn the heat an low and let it simmer for a mere minute or two until all flavors are well combined and Mozzarella has slightly melted.
Garnish with more basil if you prefer.
Notes
Use whole chicken breast and cut it in medium-size cubes (see photos). As an alternative you can use store-bough thick chicken cutlets and cut them into strips.
If using regular hard Mozzarella add an extra ¼ cup of water to the tomato sauce when cooking.
If you don't have tomato puree you can use crushed tomatoes pureed with a food processor or hand held blender.
The tomato sauce should be creamy, not too runny and not to thick.
If you're using already cut chicken cutlets you can cut them into long strips. The thinner the cut the more chicken meat will dry out so pay attention to that.
Don't let chicken sit too long in the flour as flour will start to soak the moisture of the chicken.