Place a large pot over high heat; pour the olive oil, immediately adding the mushrooms, salt and sauté, until they get a vivid gold colour in every side. Remove the mushrooms in a plate, add some extra olive oil and add the potatoes. Salt and sauté while whisking, until they also get a unified gold colour.
Lower the heat to medium, add the onion and resume cooking, until it gets slightly soft. Add half of the Cow butter, mix and add the garlic, until it is slightly roasted. Once the garlic starts smelling, increase the heat to the maximum, deglaze with the wine and cook until it is completely evaporated. Add the water, the chopped coriander, the two types of mustard and the honey. Mix, bring to a boil and lower the heat to the medium, so that the food is simmering. Cover the pot with the lad and resume cooking, until the potatoes get soft and the food remains a bit moist.
Put the mushrooms back to the pot, lower the heat to the minimum, add the rest of the Cow butter, the herbs, the spring onion, the pepper and mix, until the food starts thickening.
Taste, season to taste if necessary and serve in a large plate.