Wash the mushrooms well and chop them finely. Melt the butter in a pot, add the chopped mushrooms.
Leave on the stove to soften and release their water, while stirring periodically. In the meantime, boil the milk in a separate pot.
Once the mushrooms are ready (after 15-20 min.), season with salt and add 1 cup water. Pour in the milk to them as well.