Herb-crusted haddock with bite-sized roasties

Name: Herb-crusted haddock with bite-sized roasties
Cuisine: European, British
Ingredients: 500g new potatoes, bite sized pieces; 1.5tsp thyme leaves, roughly chopped; olive oil; 1 leek, 1cm dice; 1 courgette, 1cm dice; 1 garlic clove, finely chopped; 1 tbsp butter; 2 haddock fillets, about 150g each; 100ml creme fraiche; 40g parmesan; 20g panko breadcrumbs; 0.5 lemon, or more to taste; salt and black pepper