PREPARE THE CHICKENPlace the oven rack in the center position in your oven Preheat the oven to 450 Line a large baking sheet with parchment paper
MIx together the Dijon mustard, vinegar, salt, garlic powder, and pepper in a large bowl.
Add the chicken to the bowl and toss ingredients together to coat well.
Using a food processor or blender, add the English muffins and pulse until fine. Add the Parmesan cheese and butter and continue to pulse until combined. Transfer bread crumbs to a shallow pan or large plate.
Coat each piece of chicken in the bread crumb mixture, pressing the crumbs to the chicken so they stick and the chicken is completely coated.
Place each piece of chicken on a baking sheet, and bake until golden brown and cooked through, about 20 minutes.
Remove from oven and divide the shredded mozzarella cheese on each piece of chicken. Return to oven and continue cooking for 2-3 more minutes until cheese is melted and bubbly. Note: You can use the broiler for this step as well, with the chicken placed on the upper third of the oven, heating for 1-2 minutes until the cheese is melted.
Remove from oven and transfer chicken to plates or serving platter, topping each piece with some of the tomato sauce and garnish with fresh basil leaves.
For the tomatoes, using a large non-stick saute pan, add the olive oil and whole cherry tomatoes over medium high heat.
Cook until the tomatoes start to sizzle, shaking the pan occasionally. Continue cooking until the tomatoes start to pop and burst, crushing some of them with the back of a wooden spoon. You want the tomatoes to be soft, barely crushed and a bit saucy, total cooking time between 6-8 minutes.
Add the tablespoon of butter and stir gently to combine.
Divide tomato mixture evenly on each piece of chicken and garnish with fresh basil.