For the stock, heat the olive oil in a pot and gently sauté the onions until softened, then add the garlic and thyme and stir for a few seconds until fragrant. Add the snails and cover with water. Simmer gently for 30 minutes, then remove the snails and allow to cool. Remove the snail meat from the shells using a tooth pick and keep aside.
For the cheese sauce, heat the olive oil in a large pan or medium wok and melt in the butter. Add the garlic and thyme and allow the butter to become fragrant. Add the cream and simmer gently, allowing to reduce and thicken. Stir in the brie until melted, then scatter over the chopped parsley. Add the snail meat and a little more garlic and allow to simmer gently to warm the snails through.
For the salad mix together the cucumber, tomatoes, herbs, radishes, salad leaves and onion. Dress the salad with a splash of lemon juice and a drizzle of olive oil just before you serve it.
For the spinach, heat the butter in a pan with the garlic, until fragrant, then add the spinach and stir-fry until wilted and season with salt and freshly ground black pepper. For the bread, brush the baguette with olive oil and grill until golden. Divide the spinach between four plates and top with a little cheese sauce. Place a toasted baguette slice on top of the spinach and spoon over the snail and brie sauce. Garnish with a sprig of thyme and serve with the side salad.