Pre-heat the oven to 350 degrees F. Remove the brisket from the package into a bowl. Reserve the sauce, take the beef out and roughly chop in 1 inch pieces. Combine back with sauce. Heat an oven proof large frying pan over medium heat. Add the oil and sauté the onions and peppers and mushrooms until they start to lightly caramelize. Season with salt and pepper. Add the beef brisket and mix well. Pour the beaten eggs, mixed with a dash of milk into the frying pan and stir gently together. Place in the hot oven for 8-10 minutes until the eggs are set, add the cheese on top and return to the oven for 2 remaining minutes. Cut into wedges and serve hot from the oven.