Cut skirt steak into 4-inch long chunks and set aside.
Add garlic, salt, black pepper, 1 tablespoon vinegar, and 1 tablespoon vegetable oil to a bowl and whisk to combine. Add steak and toss thoroughly until evenly coated. Cover and marinate in the refrigerator for 2 to 12 hours. For best results, toss steaks occasionally to ensure even marination.
Before using, remove steak from marinade and use a spoon to scrape off any garlic from the surface. Place steaks and reserved garlic back in the refrigerator until needed.
Bake French fries according to package directions on a foil-lined baking sheet. The entire bag can be baked at once on a single sheet pan, but about 10 extra minutes cooking time may be needed (once baked, fries can be reserved, and reheated in a 425 degrees F (220 degrees C). oven for 10 minutes until hot and crisp).
Add remaining 1 tablespoon vegetable oil to a pan, and set heat to high. Add diced peppers and onions, and cook, stirring, until onions start to take on some color and turn translucent, a few minutes. Remove from heat and transfer into a bowl. Stir in 1 tablespoon white vinegar. Reserve at room temperature until needed.
Place the same pan back over medium-high heat, and melt 2 tablespoons butter. Transfer steaks into the pan, and cook about 4 minutes per side or until they reach your desired doneness. The heat can be turned down to medium once the meat starts to brown. When steaks are done, transfer onto a plate, and reduce the heat to low. Cover steaks loosely with foil, and set aside until needed.
Add reserved garlic to the pan, and cook, stirring, for about 30 seconds, just to take off the raw edge. Transfer in 1 tablespoon butter and 1 pinch salt; stir until melted. Turn off heat; reserve in a warm spot until needed.
For cheese sauce, add cream, cayenne, and salt to a saucepan. Bring cream to a boil over medium-high heat, whisking occasionally so it doesn't boil over. Cook for 1 minute to reduce slightly. Add in grated Cheddar and pepper Jack cheeses, turn off the heat, and whisk until cheese melts and a smooth sauce forms. Turn off heat and reserve in a warm spot until needed.
Slice steak chunks across the grain into thin strips. Stir any accumulated juices from the plate steaks were resting on into garlic butter.
To serve, divide hot French fries into 4 bowls. Top with sliced steak, and spoon garlic butter over. To finish, top with cheese sauce, pepper onion mixture, and chopped Italian parsley.
