Heat butter and oil in a large skillet over medium heat. Add carrots and onions and sprinkle with salt and pepper. Cook until tender. Add ground beef and garlic and cook until browned. Spoon off any excess grease.
Stir in peas, tomato paste, brown sugar, balsamic vinegar, and Worcestershire sauce. Sprinkle with thyme, parsley, flour and stir to combine. Slowly pour in chicken broth and bring to a low simmer and cook until gravy thickens.
Preheat oven to 400 degrees.
For The Mashed Potatoes:
Place cubed potatoes in a saucepan and cover with water and a pinch of salt. Bring water to a boil and cook until potatoes are very tender.
Drain potatoes into colander and transfer back to saucepan. Stir in butter, cream cheese, milk, salt, garlic powder, parsley and black pepper. Mash potatoes with a potato masher. Stir in half of the parmesan cheese.
Arrange Shepherd's Pie:
Add ground beef mixture to the bottom of a 4 quart dish. Top with creamy mashed potatoes and sprinkle top with remaining parmesan cheese.
Bake in preheated oven for 25 minutes until top is golden. When done, let pie cool slightly before slicing and serving. Sprinkle top with fresh chopped or dried parsley.