Ottolenghi's fennel, cherry tomato & crumble gratin

Ingredients

• 2 Fennel bulbs
• 2 tbsp olive oil
• 2 tsp fresh thyme leaves or 1 tsp dried thyme leaves
• 2 garlic cloves
• coarse sea salt
• black pepper
• enough crumble to cover
• 50 g Parmesan cheese
• 150 g cherry tomatoes on the vine if possible
• 1 tsp chopped parsley to garnish