- Portion size 6 servings
Preheat oven to 425°F (220°C).
Remove and discard mushroom stems, slice caps. In large skillet, heat oil over medium-high heat; cook mushrooms, stirring often, for 10 minutes or until liquid has evaporated.
Stir in vinegar, thyme, salt and pepper; cook for 2 minutes.
Blend mustard with 1 tablespoon (15 mL) water; set aside. Place 1 sheet of phyllo, with long side closest, on work surface, keeping remainder covered with damp towel. Brush with butter. Top with second sheet; brush with mustard. About 4 inches (10 cm) from left side, top with third sheet; brush with butter. Align fourth sheet over third; brush with mustard. About 1 inch (2.5 cm) from closest edge, sprinkle half of the breadcrumbs lengthwise into 3-inch (8 cm) wide strip, leaving 2-inch (5 cm) border at each short side. Sprinkle with 1/2 cup (125 mL) of the cheese. Arrange half of the mushrooms over cheese. Top with half each of the red peppers and asparagus; sprinkle with 1/2 cup (125 mL) of the cheese.
Fold 1-inch (2.5 cm) border over filling; fold sides over and roll up. Place, seam side down, on greased baking sheet. Brush with butter. Repeat with remaining ingredients. (Make-ahead: Cover and refrigerate for up to 2 hours; bake for 10 minutes longer.)
Bake in 425°F (220°C) oven for 25 minutes or until golden. Let stand for 5 minutes. Slice each diagonally into thirds.