Yesterday I made vanilla sauce to go with an apple pie. I used about 2 dl milk, 3 egg yolks and some sugar. I whisked it in a double boiler maybe too vigourously, because there were tiny bubbles of air in the finished sauce. It reached to correct consistency and otherwise was completely fine, but I would think vanilla sauce should have a relatively thick, rich consistency without any bubbles in it.
How can I do it better next time? Would heavy cream help? Should I not use a whisk and just stir with a spoon? How big of a risk is it that my sauce will curdle if I don't use a whisk?