Grown-Up Fish Finger Traybake

• 500 g

  baby new potatoes, halved

• 2 Tbsp.

  olive oil

• Finely grated zest and juice 1 lemon, keep separate, plus wedges to serve 

• 600 g

  frozen peas

• 3

  spring onions, chopped 

• 4

  frozen breaded cod fillets, we used Birds Eye

For the tartare sauce

• 5 Tbsp.

  mayonnaise 

• 1 Tbsp.

  capers, drained and roughly chopped

• 1 Tbsp.

  cornichons or gherkins, finely chopped

• 1 Tbsp.

  dill or parsley, finely chopped