Sauté the aromatics. Heat the vegetable oil and butter in a large sauté pan over medium heat. Add the carrot, onion, and celery. Sprinkle lightly with salt and pepper and cook for 4 minutes.

Brown the meat. Add the ground beef to the pan and cook, stirring and breaking up the beef, for about 6 to 8 minutes, until the meat is no longer pink. Stir the flour into the beef mixture and continue to cook for 2 minutes.

Add the liquids. Add the Worcestershire sauce, beef broth, and bouillon and bring to a boil. Reduce the heat and continue to cook for about 20 minutes. If too thick, add a bit more broth. Taste for seasonings and add salt and pepper, if needed. Add the steamed peas, if using, and heat through.

Prepare the tatties. Put the chunks of potatoes in a large saucepan and cover with water. Add 2 teaspoons of salt; place the pan over high heat and bring to a boil. Reduce the heat to medium-low, cover the pan, and cook for 20 to 25 minutes, or until the potatoes are tender. Meanwhile, heat the milk and butter in a saucepan or the microwave until the butter is melted.Drain the potatoes and put them in a bowl (put them through a ricer if you have one). Add the hot milk and butter mixture to the potatoes along with 1/4 teaspoon of pepper and mash until smooth. Taste and adjust the seasonings, as needed.

Serve and enjoy. Serve the mince alongside the mashed potatoes, along with butter for the potatoes and a garnish of chopped parsley, if desired.