Stir all the sauce ingredients together in a medium bowl and set aside.
Take a medium pan and place on low heat.
Add the butter to melt and add the onions and garlic to cook, until the onions are translucent and fragrant.
After a few minutes, add the mushrooms and turn the heat to high.
Sauté the mushrooms and cook.
Then add the sauce and cook, stirring occasionally. After 5 minutes of so, most of the liquid must evaporate; turn off the heat and stir in the coriander.
Warm each tortilla on a non-stick pan.
Place a few spoons of the mushrooms on each round circle.
Garnish with a coriander leaf and serve.
