Bring a large saucepan of water with 1/2 tsp salt to the boil. Peel and chop the potatoes into 2cm chunks.
When boiling, add the potatoes to the water and cook until you can easily slip a knife through, 15-20 mins.
Meanwhile, peel and grate the garlic (or use a garlic press). Finely chop the chives (use scissors if easier).
Sandwich each chicken fillet between two pieces of baking paper or cling film. Pop onto a board, then give it a bash with the bottom of a saucepan until it’s 1-2 cm thick.

Crack the egg (see ingredients for amount) into a medium bowl and whisk.
Put the panko breadcrumbs and half the Parmigiano Reggiano into another medium bowl, then season with salt and pepper and mix well.
Dip the chicken into the egg and then the breadcrumbs, ensuring it's completely coated. Transfer to a clean plate. IMPORTANT: Wash your hands and equipment after handling raw chicken and its packaging and discard any excess egg.

Pop a large frying pan on high heat and add enough oil to completely coat the bottom of the pan. TIP: You want the oil to be hot so the chicken fries properly - heat for 2-3 mins before you add the chicken.
Once hot, carefully lay the chicken into the pan, reduce the heat to medium-high and fry until golden and cooked through, 8-10 mins total. Turn every 2-3 mins and adjust the heat as necessary.
Once cooked, transfer the chicken to a clean plate lined with kitchen paper. IMPORTANT: The chicken is cooked when no longer pink in the middle.

Meanwhile, heat a drizzle of oil in a medium frying pan on medium-high heat.
Halve any thick broccoli stems lengthways, then stir-fry for 2-3 mins. Add the garlic, cook for 1 min more, then add a splash of water.
Pop a lid on the pan, or cover in foil, and cook until tender, a further 2-3 mins, then season with salt and pepper.
Once cooked, transfer the broccoli to a bowl and cover to keep warm. Wipe out the pan.

Once the potatoes are cooked, drain in a colander and return to the pan, off the heat. Mash until smooth.
Stir through the remaining cheese, half the creme fraiche and half the chives. Taste and season with salt and pepper, then cover with a lid to keep warm.
Pop the (now empty) frying pan on medium heat. Add the mustard, chicken stock paste, remaining creme fraiche and water for the sauce (see ingredients for amount), then bring to a boil and simmer until thickened slightly, 3-4 mins.

Once the sauce has thickened, taste and season if needed, then stir through the remaining chives.
When everything is ready, share the mash and broccoli between your plates.
Slice your ultimate chicken schnitzel widthways and serve alongside with the mustard cream sauce spooned on top. Enjoy!