This method refers to the stirring motion that is necessary to cook this custard over a direct heat source (flame or induction). This type of custard is fully finished in a pot on the stove top. The stirring is done with either a wooden spoon (traditionally) or a whisk. A whisk covers more area than a spoon does and thus distributes heat more efficiently and evenly.
THE STIRRED CUSTARD OR ANGLAISE METHOD IS AS FOLLOWS:
Prepare an ice water bath. In a sauce pot, combine all of the milk (or the milk and heavy cream mixture) with half the sugar and any flavorings (vanilla, cinnamon, and so forth).
Combine the egg yolks and the other half of the sugar in a bowl. The bowl should be large enough to hold all of the components of the recipe.
Bring the milk (or milk with heavy cream) to a boil. Turn off the heat, and slowly pour all of this liquid into the bowl with the egg yolks and sugar while whisking.
Return this mixture to the sauce pot and cook over medium-low heat, stirring constantly with a whisk.
Stir until the base has reached a maximum temperature of 85°C/185°F. Maintain this temperature long enough to thicken the custard until it reaches what is known as the nappé stage (anywhere between 3 and 5 minutes; it depends on the size of the batch you are making). Nappé means “coated” and what it has to coat is the back of a spoon. You are supposed to be able to run a finger through the sauce and it will leave a trace. In other words, if it were not quite yet ready to come off the stove, your finger would not be able to leave a trail, the liquid on the spoon being so loose that it would cover any trace of a trail. Evaluate the custard visually–does the custard look like it has thickened from its original state? Has it reached 85°C/185°F? Temperature and consistency are your best indicators of doneness.
Once you have reached the correct thickness/temperature, pass the liquid through a fine-mesh sieve and cool it quickly over the ice bath.
Once the custard has cooled, place it in an airtight container and refrigerate it for up to 4 days.