1. Put a large pan of salted water on to boil. Place the sun dried tomatoes in a heatproof jug and pour in 250ml boiling water. Set aside to soak for 10 mins.
2. While the sun dried tomatoes soak, peel and finely chop the onion. Trim the carrot, peel it and dice it. Trim the dry ends off the celery and dice it.
3. Warm a deep frying pan or medium pan over a medium heat for 1 min, then add 1 tbsp olive oil and the chopped veg. Season with a pinch of salt and pepper and cook, stirring often, for 5 mins till the veg start to soften.
4. While the veg fry, peel and crush or grate the garlic, pick the leaves off the oregano sprigs and finely chop them. Set a pinch of the leaves aside for garnishing. Scoop the sun dried tomatoes out of the jug (keeping the water) and finely chop them.
5. Stir the garlic, oregano and sun dried tomatoes into the veg. Cook and stir for 2 mins. Drain the lentils, rinse them under cold water and tip them into the pan. Pour in the cherry tomato passata and add the water you saved from soaking the sun dried tomatoes. Add 1 tbsp balsamic vinegar (keep the rest for later). Give it all a good stir, then bring to the boil. When the sauce is boiling, turn the heat down and simmer for 15 mins, stirring every so often, till the sauce has started to thicken.
6. While the sauce cooks, tip the pine nuts into a dry frying pan and toast over a medium heat for 2-3 mins, shaking the pan constantly, till the pine nuts are lightly toasted (they burn easily, so keep your eye on the pan). Tip into a bowl and set aside.
7. When the sauce has 10 mins cooking time left, check the pan of water – it should be boiling. Add the spaghetti and simmer for 8-10 mins till it’s cooked but not too soft, it should still have a little bounce and bite to it.
8. Whisk the remaining balsamic vinegar with 1 tbsp olive oil and a pinch of salt and pepper to make a dressing. Toss the salad leaves with the dressing.
9. Taste the bolognese sauce and add a pinch more salt and pepper if you think it needs it. Drain the spaghetti and toss with the bolognese to coat, then heap on 2 warm plates. Serve with the salad on the side, garnished with the remaining chopped oregano and the toasted pine nuts.