500g skinless fish fillets, such as haddock, cod or hake, cut into goujon-sized pieces
3–4 tbsp plain flour, plus 75g for the batter
200ml cold beer
Lemon wedges, to serve
For the Rosti Potato Cakes
600g waxy potatoes, peeled
1 tblsp rapeseed oil
Sea salt and ground black pepper
1 tblsp butter
For the Pea Mash
1 tblsp butter
200g frozen peas
1 tblsp extra virgin olive oil
Good handful of mint leaves
Preheat the oven to 180°C (350°F), Gas Mark 4.
To make the rosti potato cakes, grate the potato into a clean, dry tea towel. Gather the towel around the potato and form a small ball. Squeeze it over the sink to remove the starchy liquid. Heat the oil in a 20cm-diameter, non-stick, ovenproof frying pan over a medium heat. Season and press the grated potato into the pan so that it coats the base. Dot little lumps of butter over the top and cook in the oven for about 20 minutes.
Meanwhile, to make the pea mash, melt the butter in a saucepan over a medium heat until it is foaming. Add the peas and cook for about 4 minutes. Remove the pan from the heat and add the oil and mint leaves and then mash with a potato masher until the peas are roughly smooth. Season with sea salt and ground black pepper to taste and keep warm.
For the goujons, fill a high-sided frying pan with 2.5–5cm of oil and place it over a high heat. It needs to be very hot when you start to fry. Coat the fish in the 3–4 tablespoons of flour, shake off the excess and set aside.
Place the 75g flour in a large mixing bowl, make a well in the middle, pour in a little beer and mix through. Add the beer and mix until you have a smooth batter. Season with ground black pepper and then drop a little of the batter into the hot oil; if it floats and puffs up, it's hot enough.
Working beside the pan, dip the fish goujons in the batter one at a time and then into the hot oil. Make sure not to overcrowd the pan as this will reduce the heat. Cook them for about 4 minutes until golden brown, turning halfway through the cooking time.
Remove the goujons using a slotted spoon and place on a plate lined with kitchen paper. Season generously with sea salt and ground black pepper.
Serve with lemon wedges and a good helping of mushy mint peas and a quarter of the rosti.