Can you thicken a pudding just by reducing? Pretty simple question I hope. I am trying to recreate a recipe I made several years ago using heavy cream, lindemans framboise lambic, raspberry puree, and sugar. I don't recall using any thickeners - though I may have. It was easily 7 years ago, and the recipe is long gone, so I am trying to recreate it both from memory and based off my current culinary knowledge.

The resulting consistency was similar to a thick pudding. It worked great as a pipeable filling for cupcakes, and also was smooth and creamy enough to be a dessert on its own.

I remember reducing the cream for a long while, but as I said, I do NOT remember using any thickeners.

Is it possible if I added the fruit early on pectin would have helped thicken? If I started without the fruit and just used the lambic, cream and sugar, could I have reduced it well beyond nappe and then loosened it up with the fruit? Would that have thickened at all?

Or am I simply misremembering?

I wish I could remember what I did!
This will only thicken by reduction if you leave it on for a really long time. At least 8 hours of simmering, but better to use more than 16, and then you'll get a flavored kaymak. 

The way it thickened is much more likely to have been raspberry pectin. Many berries have sufficient pectin to thicken when they happen to be used within the optimal sugar and pH range. The calcium in the cream will also activate the second type of pectin. 

I have had raspberry juice make a jelly by itself, and I have made a recipe which thickens a gooseberry-cream mix, relying on the gooseberry pectin. I haven't made a cream based raspberry thickened dessert, but it's very likely to work. 

You can use the gooseberry recipe to get an approximate range for the sugar amount involved, http://www.bbcgoodfood.com/recipes/1415683/gooseberry-cream-and-elderflower-jelly-pots.