Bring a small saucepan of water to the boil for the peas. Peel the sweet potatoes and potato and cut into 2-3cm chunks. Put in a medium saucepan of cold salted water and bring to the boil. Reduce the heat to medium and cook for 12-14 mins until tender. Drain, return to the pan and cover to keep warm. Cook the peas in the pan of boiling water for 1 min. Drain. Reserve the pan.
Step 2 — Crumb chicken
While the potatoes are cooking, whisk 1 egg in a shallow dish. Combine 2 tbs flour and a pinch of salt in a separate shallow dish. Put the breadcrumbs in a third dish. Put the chicken flat on a board, put your hand on top and halve horizontally into fillets. Dust the chicken with the flour, shake off the excess, then dip in the egg and coat in the breadcrumbs.
Step 3 — Make butter sauce
Meanwhile, thinly slice the zucchini and set aside. Crush or finely chop the garlic. Finely chop the thyme leaves, discarding the tough stems. Melt 30g butter in the reserved pan over medium heat. Reduce the heat to low, add the garlic and thyme and cook, stirring, for 2 mins to infuse the butter with flavour. Remove from the heat before the garlic turns golden.
Step 4 — Cook chicken schnitzels
Heat 1cm oil in a medium frypan over medium heat. Cook the chicken schnitzels for 2-3 mins each side until golden and cooked through. Drain on a wire rack set over paper towel (this will keep the crumb crisp). Season with salt and pepper.
Step 5 — Cook zucchini
Stir ¾ tsp red wine vinegar into the butter sauce and return to medium heat. Add the zucchini, season with salt and pepper and cook, stirring, for 2-3 mins until the zucchini is slightly softened. Stir in the peas and remove from the heat.
Step 6 — Get ready to serve
Mash the sweet potato and potato until smooth. Add 10g butter, season with salt and pepper and stir until combined. Divide the mash, chicken schnitzels and zucchini mixture among plates to serve.