⁣First, make the Tonkatsu sauce by stirring together all the ingredients in a small bowl. Set aside to allow the flavours to develop.
Lay the pork loin fillets on a chopping board, fat side up. Tap the fillet with the back edge of a knife to create some soft notches in the meat, before pounding them on both sides with the flat side of the knife to flatten them. Slice 1cm notches into the fat of each fillet, and season on both sides with salt and pepper.
Fill a pan with the vegetable oil, and begin to heat to 180C – if you don’t have a thermometer, test the heat by sprinkling a few panko crumbs in – they should bubble and rise to the top.
Whilst the oil is heating up, you can begin the bread-crumbing process. Line up 4 plates on your kitchen counter. Put the flour on the first plate, the beaten egg on the second, the panko breadcrumbs on the third, and layer some paper towels on the fourth plate.
Take a pork loin and dredge it in flour on both sides, shaking off the excess. Next, dip it in the egg, coating on both sides. Finally, lay the fillet on the panko breadcrumbs, piling the breadcrumbs on top of the pork with your fingers and gently pressing it into the meat. Repeat for the second pork loin.
Once the oil is at temperature, carefully slide the pork loin fillets into the pan. Cook for about 4 minutes until golden, before removing from the pan with a slotted spoon and leaving on the paper-lined plate to drain.
Slice the radishes as thinly possible, preferably with a mandolin. To create the salad dressing, mix all the ingredients together, using a hand blender to emulsify, and season with salt and pepper. Dress the radishes in the dressing.
To serve, slice the Tonkatsu into 1 inch strips, and place on the plate along with a heap of the radish salad and an extra dab of Dijon mustard, if you like. Top with around 2 tbsp of the Tonkatsu sauce (or serve on the side in a small bowl).