Heat your oven to 180°C/Fan 160°C/Gas 4. Scrub the potatoes and chop them into bite-sized pieces, around 2cm across. Pop them in a large ovenproof dish. Peel and halve the shallots, then add them to the potatoes. Drizzle the veg with 1 tbsp olive oil and season with a pinch of salt and pepper. Toss to mix. Slide into the oven and roast for 15 mins.

While the veg roast, measure out 2 tsp horseradish mustard and place in a bowl. Grate in the lemon zest and squeeze in the juice from half the lemon. Season with a little salt and pepper and stir to mix. Set aside. Bend the asparagus spears till they snap. Discard the woody ends and keep the tender tips.

When the veg have roasted for 15 mins, take them out of the oven, add the asparagus tips and toss to mix. Return the dish to the oven for 10 more mins.

When the veg have roasted for 25 mins in total, take the dish out of the oven. Make 2 spaces in the veg and nestle in the cod fillets, skin side down.Brush the lemony mustard mix all over each cod fillet.

Return the dish to the oven for 10 mins, till the cod is opaque and flakes easily when pressed with the fork. The veg will be tender and browned.

While the cod and veg roast, whisk 1 tbsp aged balsamic vinegar with 1 tbsp olive oil and a pinch of salt and pepper to make a dressing. Toss the salad leaves with the balsamic dressing.

Pick the parsley leaves off their stems and roughly chop the leaves.

Serve the cod and veg with the dressed salad leaves on the side, garnished with the parsley leaves. Serve the remaining lemon half, cut into wedges, on the side for squeezing, and the leftover mustard for an extra fiery kick.