Clean mushrooms and discard stems. Slice mushrooms thinly, about 1/4" thick.
Heat olive oil over medium heat. Add sliced mushrooms and saute until brown and soft. Season with salt and pepper. Remove pan from heat and set aside mushrooms.
Heat another pan over medium heat. Brush lightly with vegetable oil. Place one tortilla in the pan and toast it until lightly browned on one side. Remove from pan. Spread generously with Scapegoat. Cover the goat cheese with a portion of the sauteed mushrooms. Spread more Scapegoat on another tortilla and place it cheese side down on the mushrooms. Brush pan with more oil, and flip quesadilla into pan so that the other tortilla can brown and the cheese can melt.
Repeat with remaining tortillas, mushrooms, and goat cheese.
Serve with guacamole, sour cream, sliced scallions, and salsa.