In a large pot or Dutch oven, heat the oil over medium-high heat. Add the onion, garlic, ginger, salt, and pepper and cook, stirring, until the onion is tender, 5 to 7 minutes.
Add the ground lamb and cook, breaking up the meat with a wooden spoon, until browned and cooked through, 5 to 7 minutes. Drain the excess fat and return the meat to the pot.
Add the cumin, coriander, garam masala, cayenne, and turmeric and cook, stirring, until the spices are fragrant, about 2 minutes.
Stir in the tomato paste. Add the beef broth and potatoes and bring to a boil. Reduce the heat to a simmer and cook, uncovered, until the potatoes are tender, about 8 minutes.
Meanwhile, make the drizzle: In a food processor or blender, combine the mint, cilantro, jalapeño, lemon juice, olive oil, salt, and pepper. Blend until smooth.
Stir the peas and lemon juice into the stew. Cook until the peas are tender, about 3 minutes.
Ladle the stew into bowls and top with a dollop of the mint chutney drizzle.