Whisk egg + 1 tbsp water in a shallow dish like a pie plate. Place all of the cutlets in the plate. Using your hands toss to coat. Wash hands.
Place cornflake crumbs, garlic powder, sesame seeds, salt & pepper to taste on a long piece of parchment/wax or butcher's paper. Mix to combine.
Using tongs grasp one cutlet at a time and dip into crumb mixture to coat on both sides. Using the back of the tongs to press the mixture onto the pork. Continue until all are coated.
Pour 1" of oil into a preheated large skillet pan on medium high heat. To test the oil, drop a pinch of crumbs into the oil. If it sizzles it is ready. Place one cutlet at a time into the pan, depending on the size of pan. Cook until golden brown on both sides. Drain on paper towel to absorb oil. Continue until all are cooked.
Meanwhile place 2 tbsp of oil in a preheated small pot add leeks add salt to taste.
Cook stirring to soften then add mushrooms and continue cooking for 1-2 min. Add the flour stir to combine, mixture will "soak" up oil. Continue to cook and stir for 1 min. Pour in the cream slowly, stirring constantly, then add mustard, pepper and taste for salt. Cook for 5-8 min. Do not allow to boil...keep it on a low simmer.
Divide between the cutlets.
Enjoy with love!