Cut out 2 tablesp. each of pea shapes of carrot and cucumber. Cook the vegetables in a little boiling stock till just tender. Melt the fat in a deep pan and stir in the flour, then the stock. Boil the stock till the flour is completely cooked, then cool it. Mix the egg yolks, milk and cream and stir them into the hot soup. Cook the egg yolks without boiling. Season and add the chopped tarragon and the cooked vegetables.