Peel and finely chop the onion, dice the carrots, and mince the garlic. Heat the vegetable oil in a large, heavy-based pot over medium heat. Add the onion and carrots and cook for around 5 minutes, stirring occasionally, until the onion softens. Stir in the garlic and cook for another 30 seconds, allowing its aroma to develop without letting it burn.

Add the minced beef to the pot, breaking it apart with a wooden spoon. Cook for 6–8 minutes until the meat is browned and no longer pink. If the mince releases a lot of fat, carefully spoon away some of the excess. Stir in the tomato purée and cook for 1 minute, then sprinkle over the plain flour and mix well so it coats the meat and vegetables.

Gradually pour in the beef stock, stirring continuously to prevent lumps from forming. Add the Worcestershire sauce, dried thyme, bay leaf, salt, and black pepper. Bring the mixture to a gentle boil, then reduce the heat and let it simmer for 15–20 minutes. The gravy should become rich and slightly thickened while the carrots soften and the flavours come together.

While the mince simmers, place the self-raising flour, suet, and salt in a mixing bowl. Add the cold water a little at a time, mixing gently until the ingredients form a soft, slightly sticky dough. Avoid adding too much water, as the dumplings should hold their shape. Divide the dough into 8 equal portions and roll each one gently into a ball.

Remove the bay leaf from the mince and stir in the frozen peas, if using. Arrange the dumplings evenly over the surface of the simmering stew, leaving a little space between them because they will expand as they cook. Cover the pot with a tight-fitting lid and reduce the heat to low. Keep the stew gently simmering rather than boiling rapidly.

Cook the dumplings, covered, for 20–25 minutes without lifting the lid too often. The trapped steam helps them rise and become soft in the middle. Check one dumpling by cutting it in half; it should be cooked through with no raw dough in the centre. Sprinkle with fresh parsley if desired, then serve the mince and dumplings hot with plenty of gravy.