Preheat oven to 375 degrees F. Generously coat a large rimmed baking sheet with nonstick cooking spray.
Place the French-fried onions in a large, sealed plastic storage bag and use a rolling pin or kitchen mallet to crush them. Measure out and reserve ¼ cup of the crushed French-fried onions for later. Place remaining crushed onions in a shallow dish (a pie plate works perfectly) and toss with flour to combine. In a separate shallow dish, combine melted butter, olive oil, Worcestershire sauce, Dijon mustard, and garlic.
Slice or pound chicken to ½-inch thickness and cut into smaller portion size pieces, if desired. Season each side with salt and pepper, to taste.
Dip chicken in oil mixture, then coat with onion mixture and place on prepared baking sheet. Drizzle each piece of chicken with about 1 teaspoon of the remaining oil mixture and then top with some of the reserved crushed onions as needed to coat chicken well.
Bake for 20 to 25 minutes or until thoroughly cooked and no longer pink in center. Cooking time will depend on thickness of chicken.
I found the French-fried onions in the canned vegetable aisle at the grocery store.