Wash the asparagus and cut off the woody ends. Peel white asparagus whole, green asparagus on the lower third. Cut 2 slices from the lemon to garnish. Cut the remaining lemon into quarters.
Bring plenty of salted water with 1 pinch of sugar, 3 tablespoons of butter and 1 lemon quarter to the boil. Cook the white asparagus for 15-20 minutes. Add the green asparagus after about 5 minutes and cook. Wash the chicken fillets and dab dry.
Heat the oil in a pan and fry the chicken fillets in it at medium heat for 10-15 minutes until golden brown. Season with salt and pepper. Pluck the chervil leaves from the stems, except for a few for garnishing.
Squeeze the remaining lemon quarters. Heat the remaining butter in a pot and brown lightly. Season to taste with salt, coloured pepper and lemon juice. Add chervil leaves. Drain the asparagus.
Cut the chicken filets into slices. Arrange on a plate with the asparagus. Pour chervil butter over the asparagus. Garnish with lemon slices and chervil and sprinkle with coloured pepper. Serve with new potatoes.