Heat oven to 350 degrees
Brown the ground beef in a frying pan.
Add the diced onion and 2 cloves of diced garlic too.
Drain any excess fat.
Add the beef broth
Add tarragon and pepper.
Reduce heat and stir.
Add a bit of the thickener and stir until broth looks more like gravy
Boil the peeled potatoes and the carrots together.
Remove the carrots from the water and chop into small pieces.
Add the peas to beef and onion mixture
Add the carrots to the browned beef, onion mixture.
Drain the potatoes and mash them
Add the sour cream and keep mashing until smooth.
In a long rectangular casserole dish, scoop and place all the beef and vegetables mixture.
Spoon mashed potatoes on top and spread them out across the length of the dish. You can make them smooth or leave little peaks on the top to brown.
Sprinkle shredded cheddar on top.
Put the dish in the oven with foil over it.
Cook for about 35 minutes, remove foil and serve.