Trim off tough part of asparagus stalk, about 2 to 8 cm from bottom. Use a vegetable peeler to scrap asgaragus to about 3 cm from top. Cut asparagus on diagonal into 3 cm pieces. Melt butter in a non stick frying pan. Add mushrooms and cook over high heat, tossing and shaking, until mushrooms are lightly browned. Add asparagus. Cook, stirring and tossing for about 1 minute. Add shallots, salt and pepper. Sprinkle with coriander. Cook for 30 seconds.