In a dish, placed in a water bath on the stove, melt the butter and mix in the liquid chocolate until homogenized. Separately, mix the eggs and sugar well and add the flour. Stir again and then mix with the chopped walnuts and coconut flakes.
Pour this mixture into a small oven dish with baking paper in it and put it to bake in a moderately heated oven for about 15 minutes. Do not bake the cake too much because it needs to remain juicy in the middle.
Optionally, brush the brownies with some extra liquid chocolate on top and sprinkle some crushed walnuts on. Put it in the refrigerator for 2 hours before you serve it.