Peel and chop the onion. Trim and dice the aubergine. Grate the carrot. Warm a frying pan over a medium heat. Add 1 tbsp oil. Add the onion, aubergine and carrot with a pinch of salt and pepper. Fry for 10 mins, stirring occasionally, till softened.
While the veg cook, peel and grate or crush the garlic. Roughly chop the tomatoes. Add the garlic to the pan and cook for 1 min.
Tip the lamb mince into the pan and break up with a wooden spoon. Fry for 5 mins till browned, stirring often. Add the chopped tomatoes. Crumble in the stock cube. Simmer over a medium heat for 20 mins, stirring occasionally, till thickened.
While the lamb mince simmers, finely shred the mint leaves. Set aside for later.
When the lamb has cooked for 10 mins, tip the penne into a pan. Pour over enough boiling water to cover. Add a pinch of salt. Cook for 8-9 mins till the pasta is al dente (soft but with a slight bite). Drain then put back into the pan. Add ½ tbsp oil. Put the lid back on to keep warm.
Sprinkle 1 tsp of the oregano into the lamb. Cook and stir for 2 mins. Taste and add more salt and pepper if you think it needs it.
Tip the cooked pasta into the lamb ragù. Fold together. Serve in warm bowls with the shredded mint scattered on top.