Pakistani-style aloo palak

Name: Pakistani-style aloo palak
Prep time: 15 min
Cook time: 1 h
Total time: 1 h 15 min
Cuisine: Asian, Korean
Ingredients: 120ml rapeseed oil; 1 teaspoon black mustard seeds; 1 teaspoon cumin seeds; 2 brown onions; 6 cloves of garlic; 3×2 cm ginger; 2 green finger chillies; 200 grams tomatoes; 1.5 teaspoon ground cumin; 2 teaspoons ground coriander; .5 teaspoon ground tumeric; 1 teaspoon kashmiri chilli powder; 2 teaspoons salt; 450 grams Maris Piper potatoes (2 medium); 1 kg frozen whole leaf spinach; 2-3 teaspoons lemon juice; Cooked basmati rice