Add milk and coffee beans to a medium saucepan and bring to a boil over medium heat
Turn the heat to low, cover, and let the coffee beans steep for 20 minutes. Stir occasionally
Meanwhile, beat the sugar and egg yolks in a medium bowl until they're thickened and light yellow in color
Beat in the flour and salt and set aside
Remove some of the coffee beans with a slotted spoon and then pour the mixture over a strainer and into a liquid measuring cup
Some of the milk probably evaporated so add fresh milk back until it measures to 1 1/2 cups again
Slowly beat the warm milk into the eggs and sugar, constantly whisking
Once all the milk is incorporated, add the mixture back to the saucepan and set the heat to low
Stir constantly until the mixture thickens enough to coat the back of a spoon (don't let it boil!)
Once it has thickened, pour the mixture through a fine mesh strainer into a separate bowl
Allow the mixture to cool to room temperature and then stir in the heavy cream and vanilla
Cover with plastic wrap and refrigerate for a few hours or overnight (I always do overnight)