Gelato-style vanilla base recipe à la Fernanda Gosetti, found in the classic book "Il Gelato".
Ingredients
5 egg yolks
125 ml sugar
450 ml milk
100 ml cream
1 vanilla bean (note that the original recipe only calls for ¾ bean, so if you prefer a milder tone of vanilla, you may want to cut back to that)
Instructions
Whisk together the egg yolks and sugar in a bowl.
Cut the vanilla bean lengthwise, scrape out the small seeds and put all together with the milk and the cream in a saucepan. On low heat, bring to a close boil. Remove the vanilla bean stalk-pieces (but keep them on the side - they'll be reinserted later!).
Slowly and little by little, pour the hot milk/cream into the egg-sugar mixture, whisking all the time ("the tempering stage").
When the ingredients have been mixed, pour back the liquid into the saucepan.
On low heat, continue to whisk, ultimately bringing the mixture up to about 82-84º Celsius (189-183 ºF); the stage when you should be able to draw a line through the custard on the back of a spoon (or equivalent) that stays. For added security, use a thermometer! And remember to whisk all the time - you don't want to end up with scrambled eggs!
Take off from the heat, put in the vanilla beans again and cool down the ice cream base as fast as possible. When sufficiently cool, put in a refrigerator to chill for about five hours (or preferably, over night).
Remove the vanilla bean-parts and pour the chilled ice cream base in your ice cream machine and churn according to instructions.
Store the ice cream in a freezer-safe container with lid, making sure to cover the surface with plastic film before putting on the lid.
Notes
In case you plan on using this ice cream as a base for other flavours/ingredients, you should consider if those added ingredients will add a lot of sweetness. If so, you may want to reduce the quantity of sugar in the base recipe (in order to avoid too overly sweet end-results).
Recipe by ICE CREAM NATION at https://www.icecreamnation.org/2012/05/gelato-vanilla-base/