Grease a 22 x 22 cm baking pan with the butter. Preheat the oven to 180 ° C.
Whisk all ingredients together well and season with salt and pepper. Place in the baking pan and bake for 30 minutes until the mixture has set. Take out of the oven.
Carefully tip out of the mold and cut into pieces of the same size. Serve warm or at room temperature.