First thing to note – the recipe is a bit strange. I added some oat bran to the custard base, both to add a little nutritional value and to see how it affects the texture as a thickener.
So the ingredients were as follows:
250 g milk
70 g oat bran
50 g maple syrup
50 g sugar
25 g NFDM
1 XL yolk, 18-19 g (this might be part of the problem, too little yolk)
1.5 tsp freeze-dried coffee
1/2 tsp vanilla extract
Maybe 0.5 g of salt
0.5 g xanthan gum
0.5 g guar gum
+ (later on)
250 g whipped cream
The process was:
In a pot, I mixed all of the ingredients except for the heavy cream, brought to a simmer while mixing and kept going for another 30 seconds. Removed from heat, transfered to a Pyrex bowl, and after it had slightly cooled I blended with an immersion blender. I placed it in the freezer for almost a full day (it didn't actually need so many hours but I just didn't get back to it).
After that I took the base out of the fridge, let it warm up for a few minutes and started carving it out. I whipped heavy cream and placed it for a moment in the freezer as I finished getting the frozen base better mixable. I then folded in the whipped cream until it looked fairly mixed-together while trying to keep most of the air inside.
I put the finished thing back in the freezer and after 12 hours it's still pretty scoopable as soon as you take it out (definitely more than Ben & Jerry's, for example). Texture-wise it's okay (although the bran would've benefited from being "mealed" in advance), but it is a bit icy if you bite through it.
One thing I could've probably improved is the initial freezing time: not having the base frozen for this long before adding the whipped cream should have made the "carving" process easier and more thorough. The other thing is the ingredients: I used maybe 1/3 the amount of yolks many recipes recommend. I did use stabilizers/thickeners, but perhaps that's not enough (and not "the right kind") to replace a proper amount of yolks?
What are your suggestions? Thanks.