Place the mushrooms, onion, chile, broth or water, lime juice and lard or other fat in a medium-size saucepan. Bring to a boil over medium-high heat, cover and cook 3 minutes. Uncover and cook until all the liquid has evaporated and the mushrooms begin to fry in the fat.
While the mushrooms are cooking, puree the tomato with the garlic in a blender or food processor. When the mushrooms begin to fry, add the tomato mixture and optional epazote and cook until the liquid has reduced and the mixture is thick, about 5 minutes. Season with salt (usually 1/2 teaspoon, depending on the saltiness of the broth) and scrap into a serving bowl. Serve with tortillas on the side for making tacos.