This is what you need to prepare. Double boiler(Bain marie), bowl of ice water, a whisk, a hand blender and a bit of cold milk at hand.
If your bowl doesn't have handles. You can always make a long band of foil to put under the bowl. very important to b able to take off the bowl quickly if the cream becomes too Thick..It goes fast
In the cooking bowl. You can mix all ingredients together and put it over the hot water bath OR.. Heat the milk and add over eggs sugar while mixing then put over the hot bath. Continue to whisk➡️➡️
It is thick enough to coat the back of a wooden spoon and leave a trail
If your bowl doesn't have handle.. Fold a long sheet of foul and put it under the bowl while heating. It is essential to b able to take out the cooking bowl very quickly when sauce is thick.
Put the bowl in the ice bowl and continue to whisk until cooled down
As last precaution or tip. Use your hand blender to smooth out any eventual lumps or over thickened parts.
Hit is thick enough to coat the back of a wooden spoon and leave a trail
Cover with a plastic film in contact with the cream so as to prevent a crust forming