Melt 1 tablespoon butter over medium-high heat in large skillet . Add mushrooms, onion and garlic; cook 7 minutes or until vegetables are tender and liquid is evaporated, stirring occasionally. Remove from heat; cool slightly.
Stir 1 cup cheese and lemon pepper into cooled mushroom mixture; spread 1/3 cup mixture onto each chicken breast. Fold chicken lengthwise in half; secure each with 2 wooden picks. Melt remaining 2 tablespoons butter; dip chicken into butter and roll in crumbs. Place in lightly greased shallow baking dish or pie plate; drizzle with remaining melted butter.
Bake in preheated 450°F oven 20 minutes or until golden brown and chicken is cooked through. Sprinkle with remaining cheese. Bake 3 minutes more or until cheese is melted. Remove wooden picks before serving.