I agree with Thermomixer, CP. Scalding works at 90, 100 is too much. I cut the vanilla beans into 2-3cm strips and score them vertically with a sharp knife. The seeds seem to come out the with mixing. I've found with ice cream the "all in at once" approach doesn't really get the results I want. So what I do now is mix the egg yolks and sugar in my Kitchenaid until they're really fluffy - I can't get the same result with the butterfly in the TMX - while I am heating the milk/cream mixture. I then pour some of the hot milk/cream into the kitchenaid, mix it a little, and then pour that back into the TMX jug. I then mix that on 80 rather than 90. If you use 90 for thickening the custard, you have to practise and get your timing perfect otherwise it will curdle. Unfortunately this seems to vary with the eggs, the ambient room temperature, everything. I find it too annoying. So I use 80 and mix for longer than recommended, sometimes it takes 12-15 minutes to thicken enough but at least it won't curdle. Heston Blumenthal, who is a chemist as well as a chef, reckons the custard only needs to go to 75 anyway for a better texture and I think from mucking around with my TMX he's probably right.
If I'm in a hurry I mix the egg and sugar in the TMX with the butterfly on 5 at temp 50 as Thermomixer has previously suggested, then add the milk/cream. It's a denser mix than I like, I just don't think as much air gets in as the above method. But for convenience, you can't beat it.
Speaking of icecream, I can't wait for mango season. A couple of mangoes, some cream, sugar, lime juice and a bit of white rum blitzed together is going to make a very nice quick icecream.
