Slice meat into 1/2-thick by 2 -nch long very thin strips and season with salt and pepper. Set in freezer.
Heat a skillet over medium heat. Melt 2 tablespoons butter and cook with flour 1 minute. Whisk in consomme. Thicken 1 minute. Stir in mustard and sour cream, thicken 2 to 3 minutes. Remove from heat and season sauce with salt and pepper.
Heat a second skillet over high heat. Add 1 tablespoon oil and 1 tablespoon butter, then add the meat and onion and cook over high heat until brown on both sides, 3 to 4 minutes total. Then add the chopped cornichons and stir to combine.
Arrange meat on a bed of egg noodles and top with Stroganoff sauce and parsley. Serve with thickly sliced pumpernickel bread.