You won't miss the fat in this lightened up version of this classic English casserole
Preheat oven to 350°F, using convection roast if setting is available
Prepare mashed potatoes – Wash potatoes, place in a pot, add a generous salt pinch, cover with water, and boil covered, until potatoes tender, about 15-20 minutes, and pierce easily with a fork
Meanwhile, prepare the base meat layer by sautéing onion, garlic, and thyme in olive oil in a medium skillet until onions begin to soften, about 5 minutes, then stir in black pepper, tomato paste, and tamari
Add mushrooms and sauté for 5 minutes, stirring occasionally
Add beef and break into crumbles with a spatula, stirring to combine
When meat is cooked through, taste to adjust seasoning as needed, stir in corn starch or sweet rice flour, and place meat mixture in a 9x9 baking pan
Evenly spread a layer of diced carrot and peas on top of meat mixture
Drain potatoes, reserving 2 cups cooking liquid
Place potatoes back in pot, add milk, salt, pepper, rosemary, and scallions
Mash potatoes to a desired consistency, thinning with reserved potato cooking liquid if needed
Taste to adjust seasoning, and spread potatoes on top of meat mixture in baking pan
Top with grated parmesan cheese, then sprinkle generously with smoked paprika
Bake uncovered until potatoes are browned, and meat is bubbling, about 30 minutes
Use a spatula to cut into squares, and serve with a simple green vegetable like steamed broccoli or a salad
You can make this vegetarian by substituting veggie crumbles for ground beef