Wash, peel and halve the asparagus. Cook the asparagus in boiling salted water for about 10 minutes. Drain and place in a bowl. Pour over 4 tablespoons of oil and marinate for about 1 hour. Meanwhile wash the chervil, dab dry and chop finely.
Peel the shallot and cut into fine cubes. Heat 1 tablespoon of oil in a pan. Sauté the shallot. Knead butter with chervil, warm shallot and salt. Put it in a cold place. Remove asparagus from the marinade. Fry briefly on a very hot grill pan. Cut baguette into slices. Arrange chervil butter, asparagus and baguette slices.
Put it in a cold place. Remove asparagus from the marinade. Fry briefly on a very hot grill pan. Cut baguette into slices. Arrange chervil butter, asparagus and baguette slices. Garnish with lemon slices and chervil