Pre-heat oven to 400°F.
In a Dutch oven, saute carrots in the olive oil until starting to get tender.
Add in the onions and saute for a minute or two then add the meat.
Season with black pepper and thyme.
Cook until browned then drain fat.
Add the butter and peas.
Sprinkle with flour and stir through.
Add tomato paste, wine and Worcestershire sauce.
Let this reduce slightly then add the chicken stock. Allow to reduce down until you have a thick meaty gravy. Season to your taste.
Remove from heat.
Grease an oven proof dish and add the sauce.
Spoon or pipe the mashed potatoes over top. Brush with egg and sprinkle with Parmesan cheese if using.
Bake for about 20 minutes or until the potato is nice and browned on top.