Bring medium pot of salted water to a boil.
1) Wash and quarter cut potatoes
2) While potatoes cook. Brown hamburger with onions.
3) Add 1 Tbs butter and allow to melt. Add flour. Stir to combine. Add in tomato paste, Worcestershire sauce, thyme, rosemary, garlic and 1/2 cup beef stock. Cook for 1min.
3) If meat mixture needs to be thinned, use a small amount of the potato water.
4) Heat peas and carrots and add to the mixture.
5)Pour mixture into medium size baking dish.
6) Drain potatoes reserving 1 cup of water. Return potatoes to pot and add remaining butter, sour cream salt and pepper to taste. Do a rough mash of potatoes and add in the white cheddar cheese. Use some of the reserved water if potatoes appear too dry. Mix well and spread potato mixture over meat mixture.
7) Heat in oven for 20 mins . Broil for the last 5 to brown.