Finely chop the garlic and the courgette.
Heat the olive oil in a large frying pan and gently sauté the mushrooms over medium heat for about 5 minutes. Add the garlic and courgette, then pour in the balsamic vinegar and let it sizzle for 30 seconds. Cover and cook for a further 5 minutes, under cover, until the veggies are slightly caramelised.
Add the lentils and stock, bring to the boil and cook for another 5 minutes, until the vegetables are tender and the sauce has reduced.
Stir in the lemon juice and the parsley.
Season to taste, then serve immediately with a dash of lemon juice.