Sweet Potato Satay Curry

Name: Sweet Potato Satay Curry
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: Asian, Indian
Ingredients: 500g / 17.6 oz. sweet potatoes about 1 large or 2 small; 70-100g / 2-3 cups baby spinach; 1 onion; 4 cloves of garlic; a small piece of ginger about 1-2 cm / ½ inch; 1 tablespoon curry powder (spice blend); ½ teaspoon cumin; ½ teaspoon turmeric; ¼-½ teaspoon chilli flakes optional; 1-2 stalks lemongrass optional, or 1 drop essential oil, see notes; 1 tin coconut milk 400ml / 13.5 oz.; 2-3 tablespoon peanut butter; 1 tablespoon coconut aminos or soy sauce; 1 lime (juiced) optional