Minted Lamb Pasties

Name: Minted Lamb Pasties
Ingredients: 75g (2½ oz) salted butter, chilled and cut into 1cm/½in cubes; 75g (2½ oz) lard, chilled and cut into 1cm/½in cubes; 200g (7 oz) plain flour, sifted, plus extra for dusting; ½ tsp salt; 1 tsp lemon juice; 1 large free-range egg, beaten, for egg wash; bunch of fresh mint, leaves picked; pinch table salt; 1 tbsp caster sugar; 50ml (2 fl oz) white wine vinegar; 100g (3½ oz) lamb leg steak, diced into 1.5cm/⅝in cubes; 1 garlic clove, crushed; ½ tsp dried rosemary; salt and freshly ground black pepper; ½ large red onion, finely chopped; ½ large sweet potato, chopped into small cubes; 1 medium carrot, chopped into small cubes; ½ bunch fresh flatleaf parsley, leaves picked and chopped; ½ tsp dried oregano; 50g (2oz) frozen peas, defrosted