Heat oil in a dutch oven over medium heat. Add ground lamb, potatoes, onion, and Serrano pepper. Cook for 10 minutes, stirring occasionally, or until the meat is fully browned. Add garlic, rosemary, salt, and pepper, cooking for 1 or 2 minutes until fragrant. Cover with a lid and cook until the potatoes are tender. Add the paprika and turmeric and mix well before serving.