I followed the recipe as given (a basic creme anglais with vanilla; marzipan pureed in after cooking), except that I
1) simmered some chopped, blanched, untoasted almonds in the milk/cream mixture the night before and let it sit overnight. Tasted the mixture the next day, just the slightest hint of almond flavor. Not worth doing, and certainly would not serve as the basis for an almond-flavored ice-cream.
2) Only used a few drops of vanilla extract (didn't want to muddy the almond flavor.) Used Penzey's almond extract instead.
3) Used almond paste instead of marzipan, then added just a tablespoon of sugar.
I didn't strain it well, because I didn't have a fine enough strainer. That was the big mistake.
The marzipan flavor came through marvelously - just like eating marzipan, except it's not so shameful to eat a whole bowl. The problem was that it was definitely gritty. A chinois would take care of that in no time flat. But I didn't have one. Sigh. Also, as ice creams go, you don't get much more expensive. (About 6 dollars on the almond paste alone). But I will make this again once I break down and buy a chinois.
Ended up using the almond cake from Nick Malgieri's How to Bake, substituting white sugar for the brown. because I was serving with cherries and wanted something a bit more delicate.
Now I'm imagining a rum flavored ice cream with dried dates and some sort of clove-crumble....