
Add a few tablespoons of olive oil and sauté the sliced mushrooms and shallots on medium-high heat until tender and golden brown. Then add garlic and cook for 1 minute.
Add a tablespoon of Dijon mustard to the mushrooms and the cold water. Stir until the mustard is incorporated and the sauce begins to forms. Add butter and stir. Add the fresh thyme.
If you need to add more water, add it by the ¼ cup, and Dijon by the tablespoon.