While the coffee beans steep, beat the sugar into the egg yolks in a medium mixing bowl, until they’re thickened and pale yellow. Beat in the flour and salt. Set aside.
Remove the coffee beans with a skimmer or slotted spoon, or pour milk through a strainer catching the coffee milk on the other end. If some of the milk has evaporated, measure it out and add more fresh milk to make 1 & 1/2 cups if milky coffee.
Slowly beat the warm milk into the eggs and sugar. Pour the entire mixture back into the pan and place over low heat. Stir constantly with a whisk or wooden spoon until the custard thickens and coats the back of a wooden spoon. Be careful not to let the mixture boil, or the eggs will scramble. Remove from heat, and pour the hot coffee custard through a strainer into a large, clean bowl. Allow the custard to cool slightly, and stir in the cream and vanilla. Cover and refrigerate until cold or overnight.