Preheat oven to 375 degrees,
Place potatoes in medium stock pot & cover with water.
Boil until fork tender (approx. 25 minutes)
While potatoes boil, add ½ T oil to skillet & brown ground beef on med-high heat.
Add onion, garlic, peppers, 1/2 salt, herbs & spices once meat is browned. (approx. 10 minutes)
Add balsamic, 1/2 T. butter & mushrooms. Cook 5 minutes.
Place ground beef mixture in casserole dish & layer raw vegetables on top of meat.
When potatoes are done, drain & reserve about ¼ cup liquid & set aside.
Add 2T. butter & ¾ tsp salt to potatoes & mix with hand mixer. Add water if needed.
9 Layer sweet potatoes into casserole dish & bake 30 minutes.