Roast the onion cubes in 1 tablespoon butter, add the cleaned chanterelles, season and steam until the liquid has evaporated. In the meantime, whisk the eggs with flour, baking powder, milk and salt into a smooth batter. Place the mushrooms on a plate, wipe the pan with a kitchen towel and melt the remaining butter in it. Pour half of the batter into the pan, spread the mushrooms over it and pour the rest of the batter on top. Cover and over medium heat (not too hot, otherwise the dough will burn and not too cold, otherwise the mixture will not rise) bake for about 6 minutes, turn and finish baking. Tear into pieces with two forks, sprinkle with chives and serve with tomato slices. Leaf salads go well with it.