Preheat oven to 400. Peel and dice potatoes. Add to a saucepan and cover with water. Bring to a boil and boil 5-7 minutes or until the diced potatoes are soft.
Drain potatoes and transfer to a large bowl along with butter, rosemary, thyme, salt and pepper. Mash with an immersion blender or transfer to a food processor (or mash by hand with a fork).
Brown beef in a skillet or medium saucepan and then remove from pan. Set aside. In the same pan, saute onions, celery, carrots and mushrooms. Saute 6-8 minutes.
Add beef, peas, garlic, broth, paste, liquid aminos, salt, and pepper to the pan. Stir well, and bring to a boil. Reduce heat and let simmer 10-15 minutes.
Transfer filling to a greased baking dish. Top with sweet potato mixture. Sprinkle with paprika. Bake at 400 for 25-30 minutes.