Steps

• Peel and thinly slice the onion. Peel the garlic cloves and roughly chop them. Thinly slice the mushrooms.
• In a saucepan, heat the margarine over high heat. Sauté the onion and garlic for 2-3 minutes, stirring occasionally. Add the mushrooms and rosemary. Cook on high heat for about 7-8 minutes until everything is nicely browned and grilled.
• Deglaze with the tamari and then add 1 liter of water. Let it simmer for 20 minutes so that all the flavors infuse.
• Strain the mixture to keep only the juice*. In a bowl, whisk a small portion of this juice (about 1/4) with the cornstarch. Combine with the remaining juice and heat again in a saucepan, whisking to thicken the sauce. When it reaches the desired texture, remove from heat and add pepper. Taste and adjust seasoning as needed.

Notesyou can keep the rosemary-cooked vegetables so as not to waste them, they can be served as a side dish or blended into a mushroom soup.