Enchilada Sauce: Heat oil in a wide frying pan over medium heat; add onion and cook, stirring, until soft; stir in remaining sauce ingredients; bring to a boil, cover, reduce heat and simmer for 10 minutes.
Enchiladas: In a wide frying pan over medium heat, melt butter; add mushrooms and cook, stirring, until mushrooms are golden and liquid has evaporated.
Reduce heat to low and add chiles, onions, yogurt, cream cheese and flour; cook, stirring, until mixture boils and thickens; remove from heat.
Bring enchilada sauce to a boil over medium-high heat; then remove from heat; using tongs, dip a tortilla into bubbling sauce for a few seconds to soften, then place in a greased 9x13-inch baking dish; spoon about 1/2 cup of the mushroom mixture down the center of each tortilla and roll to enclose; arrange seam side down; repeat until all tortillas are dipped and rolled; if sauce becomes too thick, thin it with water or wine.
Pour remaining sauce evenly over enchiladas; bake, covered, in a 375°oven for 20 minutes; uncover and sprinkle with cheese; continue baking, uncovered, for 5 more minutes or until cheese is melted.