Brush the bread slices thinly with butter. Cut the mozzarella into 12 slices, the anchovies into small pieces and the tomatoes into slices or small cubes.
Top each baguette with a slice of mozzarella and a few pieces of anchovies as well as a tomato slice or a few tomato cubes. Place the bread slices on a baking tray lined with baking paper and season with a pinch of oregano and salt and pepper. Drizzle with a little olive oil.
Bake in the oven preheated to 200 ° C for 7-8 minutes until the mozzarella has melted. Serve warm.