Place milk in a saucepan, fish stock, and cream and bring to the boi. Turn down to simmer and add the haddock. Poach for 6 to 8 minutes until cooked, remove and set aside.
In a skillet, melt the butter and stir in the flour, stirring continuously, let it cook for 1-2 minutes.
Gradually add the cooking liquid, making sure you continue to stir well.
Add the 150g of cheddar along with pepper.
Butter an ovenproof dish and rub with the garlic clove.
Place the poached haddock from earlier on top of the spinach, with the halved cherries, tomatoes surrounding the fish.
Top with the cheese sauce and sprinkle with both the bread crumbs and thyme leaves.
Scatter the remaining cheese on top and grill until golden.