Heat the olive oil in a large pan and cook the onion over a medium-high heat for 5–6 minutes, until softened.
Meanwhile, cook the carrots in a pan of lightly salted boiling water for 5–6 minutes, until just tender, adding the peas for the final 2 minutes. Drain.
Add the tomato purée to the onions and stir for 1 minute. Mix in the beef, stock, Worcestershire sauce and thyme (if using). Stir in the carrots and peas, then simmer for 2 minutes, until thickened slightly. Spoon over the grilled waffles to serve.