Pound out the chicken (or use storebought thin sliced cutlets), cut into 5” pieces, and season with salt and pepper on both sides. Dredge the chicken in flour and shake off excess.
Heat a large pan to medium heat and wait 2 minutes. Once the pan is hot, add a couple of tablespoons of olive oil and sear the chicken on both sides (about 2 minutes per side). Work in batches. Use more olive oil as required. Set all the cooked chicken aside and tent with foil to keep warm.
Next, add in the mushrooms and cook until they release their water and brown (about 5-7 minutes). Place the mushrooms on a plate and set aside.
Next, add the peppers to the pan. Cook them until soft (about 10 minutes), then add in the garlic and cook for a few minutes more until the garlic turns lightly golden. If using the wine, add it now and cook the alcohol out for a few minutes. With a wooden spoon scrape any brown bits off the bottom of the pan.
Add in the tomato paste and cook for 5 minutes with the peppers and garlic stirring frequently. Add in the plum tomatoes, oregano, and mushrooms, and bring the sauce to a simmer. If the sauce is too thick add a bit of water (4-6 ounces or so) and stir together.
Taste test the sauce and adjust salt, pepper, and oregano to taste. When satisfied with the taste return the chicken to the pan and cook for a few more minutes to warm it through.
Turn off the heat and add in the basil and a hefty drizzle of high-quality extra virgin olive oil. Serve with crusty Italian bread to mop up the sauce. Enjoy!