01 - Preheat the oven to 400°F.
02 - Place sweet potatoes in a large pot, cover with cold water, add a pinch of salt, and bring to a boil. Simmer for 15–20 minutes until very tender.
03 - Drain the sweet potatoes and mash with butter and milk. Season with salt and pepper to taste. Set aside.
04 - While sweet potatoes cook, heat olive oil in a large skillet over medium heat. Add onion, garlic, carrots, and celery; cook 5–7 minutes until softened.
05 - Add ground beef; cook, breaking it up, until browned and cooked through, about 8–10 minutes.
06 - Stir in tomato paste, thyme, rosemary, smoked paprika, and season with salt and pepper. Cook 2 minutes.
07 - Add peas, beef broth, and Worcestershire sauce. Simmer for 5–7 minutes until slightly thickened.
08 - Transfer the beef mixture to a large baking dish. Spread the sweet potato mash evenly over the top.
09 - Use a fork to create ridges on the mash for a crispy finish.
10 - Bake for 20–25 minutes, or until the top is golden and filling is bubbling.
11 - Cool for 5 minutes before serving.