Preheat oven to 350 degrees. In a food processor chop the garlic one piece at a time. Add the tomatillos, cilantro and chiles and process until smooth.
Heat the 1 1/2 tablespoon oil in a medium saucepan over medium high heat. Add the puree and cook stirring nearly constantly until the mixture has reduced to the consistency of thick tomato sauce. About 10 minutes.
Add the chicken broth and simmer over medium heat for another 10 minutes.
While the sauce is simmering, heat the remaining 1 1/2 tablespoons of oil in a large skillet over medium high heat. Add the mushrooms and cook until they begin to brown.
Add about three quarters of the onion and reserve the rest for garnish. Cook, stirring frequently until the onion looks translucent. Add the spinach and chicken and cook for a minute or so, until the spinach is wilted. Season with salt. Cover to keep warm.
Lay out the tortillas on a baking sheet and brush lightly on both sides with olive oil. Stack them in twos and slide them into the over an bake just long enough to where they are soft. About 3 minutes. Remove from oven and stack them in a single pile and cover with a kitchen towel to keep warm.
Stir the creme into the tomatillo sauce. Taste and season with salt and sugar.
Spoon a heaping tablespoon of the sauce onto a warmed plate. Hold a tortilla by one edge and dip most of it into the sauce and lay it on the plate. Spoon a heaping 2 tablespoons of the filling down the center, roll up and positioning the enchilada seam side down. We did two enchiladas per plate.
Douse the enchiladas with 1/4 cup of the warm sauce and sprinkle with crumbled cheese, sliced onion and chopped cilantro. Serve immediately.