Wash the oysters in salted water, changing the water 2–3 times, then drain and pat dry. Cut spinach into 3cm lengths and slice bacon into 1cm strips.

Pat dry the oysters, season with salt and pepper, and coat with all-purpose flour.

Heat olive oil and half the butter (10g) in a frying pan. Add oysters and bacon, cooking over medium heat until oysters are browned and cooked through. Remove from the pan.

In the same pan, heat the remaining butter (10g) and sauté spinach over medium heat until wilted. Season with salt and pepper.

Slice the French bread thinly and layer it in a large gratin dish. Top with sautéed spinach and cooked oysters and bacon.

Mix heavy cream and milk in a bowl, then pour over the layered ingredients. Sprinkle shredded cheese and breadcrumbs on top. Bake in a preheated oven at 250°C for about 15 minutes until golden brown.