Peel the asparagus spears and cut the woody ends into small pieces. Cook in about 3/4 liter of boiling salted water with a little sugar for about 20 minutes with the lid closed.
Cut peach halves into 4 to 6 wedges each. Toast bread and spread each with 1 tsp butter. Roughly grate cheese.
Remove asparagus spears and measure out one-eighth of a liter of asparagus water. Mix in contents of bag and bring to boil. Gradually fold in 125 g butter in pieces over low heat. Add cheese and let it melt in the sauce. Season with lemon.
Place breads on a baking sheet. Top with ham, asparagus spears and peaches. Spread sauce evenly over the top. Bake in hot oven (electric oven: 225 °C /gas mark 4) for 10 minutes until golden brown. Arrange on a platter. Garnish with tomatoes, lemon and chervil.
Tip: It is best to use your favorite ham – then your dish tastes twice as good!