1) Preheat the oven to 180 °C 2) Pour the olive oil into a large frying pan over a medium heat. Add the bacon and leeks, and sauté until cooked. Approx 5 -7 minutes. 3) Meanwhile make the cheese sauce; add the milk, butter and flour to a large saucepan and whisk until thickened. 4) Add half the cheese and allow to melt, season to taste. 5) Add the leeks, bacon and cauliflower to the cheese sauce and stir through. 6) Add the spinach to the now empty frying pan and allow to wilt. Add to the cheese sauce and stir through. 7) Check the seasoning. 8) Pour into an oven proof dish, top with the remaining cheese and bake for 30 minutes or until cauliflower is cooked to your liking.