Peel the potatoes and cut into large chunks. Thinly slice the onion. Thinly slice the carrot on an angle. Crush or finely chop the garlic. Crumble 1 stock cube* into a heatproof jug, add the worcestershire sauce and 180ml (¾ cup) boiling water and stir to dissolve.
Step 2 — Make mash
Put the potato in a medium saucepan of cold salted water and bring to the boil. Reduce the heat to medium and cook for 10 mins. Add the peas and cook for a further 2 mins or until the potato is tender. Drain. Mash the potato and peas until the potato is smooth. Add 2 tbs milk and stir until combined. Taste, then season with salt and pepper. Cover to keep warm.
Step 3 — Brown beef
Meanwhile, separate the beef stir-fry. Heat 1 tbs olive oil in a large frypan over high heat until very hot (beef stir-fry is best with hot, fast cooking; get the pan very hot before adding the beef and stick to the short cooking time). Cook the beef, stirring, for 1-2 mins until browned. Remove from the pan with a slotted spoon, reserving the oil in the pan.
Step 4 — Start onion gravy
Return the pan to medium-high heat and add 2 tsp olive oil. Cook the onion, carrot and garlic, stirring regularly, for 4 mins or until the onion is golden and softened. Scatter over 3 tsp flour and cook, stirring constantly, for 1 min or until lightly browned.
Step 5 — Finish onion gravy
Gradually add the stock, stirring constantly to prevent lumps forming and bring to the boil. Reduce the heat to medium and cook, stirring regularly, for 3-4 mins until thickened and the carrot is tender.
Step 6 — Get ready to serve
Add the beef and any resting juices to the gravy and cook, stirring, for 30 secs or until heated through. Taste, then season with salt and pepper. Divide the mash and beef mixture among plates to serve.