Place the flour in a large bowl and season generously with salt and freshly ground black pepper.
Place the breadcrumbs in a large flattish bowl and mix in the chopped thyme and sage.
Dredge each pork escalope lightly in the flour on both sides, shaking off any excess, then submerge in the beaten egg and press into the breadcrumb mixture, coating on both sides.
Heat a little of the the oil in a large frying pan over a medium heat and fry the schnitzels in batches for 2-3 minutes on each side, or until golden-brown and completely cooked through (there should be no trace of pink in the middle). Remove the schnitzels from the pan and set aside to drain on kitchen paper. Cook the remaining escalopes, adding more oil as necessary.
For the sauce, melt the butter in a large saucepan, then add the flour and cook for 2-3 minutes. Slowly add the milk to the pan, whisking continually, until you have a thick white sauce. Season with salt then add the parsley and cook for a further five minutes.
Serve the schnitzel with a spoonful of the sauce and vegetables of your choice.