Combine the milk and coffee beans in a heavy medium saucepan. Bring to a boil over medium heat. Lower the heat, cover, and keep warm for 20 minutes.
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 of 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.
Stir the chilled custard, and freeze in your ice cream machine, according to manufacturer’s instructions. When finished, the ice cream will be soft, but ready to eat. For firmer ice cream, transfer to a freezer safe container and freeze at least 2 hours.