This recipe was taken from the book Cooking the Austrian Way.

Ingredients:

2 lemons
1/2 cup sugar
a few grains of nutmeg
1 Tblsp butter
2 Tblsp flour
2 cups boiling water

Melt the butter and then slowly blend the flour into it. Do not let the flour get the slightest bit brown. Very gradually, with constant stirring, pour in the hot water, and continue stirring until well blended and the sauce is beginning to thicken. Grate the rinds of the 2 lemons into the sauce, then add the juice of one of them. Add the sugar, and the nutmeg. Remove the saucepan from the heat. Scoop out the flech from the second lemon and add these juicy bits to the sauce. Use either hot or cold.