Fish pie tart with minted pea salad

Name: Fish pie tart with minted pea salad
Ingredients: 500g pack shortcrust pastry (or make your own), see tip, below left; 1 egg yolk and 3 whole eggs; 250g piece undyed sustainably sourced smoked haddock; 250g chunky unsmoked fish (we used sustainably sourced cod); 200ml tub crème fraîche; ½ pack chives snipped; grating of fresh nutmeg; handful of cooked sustainably fished large prawns defrosted if frozen; 25g sharp cheddar or similar cheese, grated; 250g frozen petits pois; 2 x bags baby leaf salad with pea shoots in the mix; mint; 2 shallots finely chopped; ½ tsp sugar; 2 tbsp red wine vinegar; 2 tbsp extra virgin olive oil; 1 heaped tsp wholegrain mustard