I provide fondant above a feed hole in the crownboard from Christmas but they might not touch it until late January or after. At the moment (late Feb) this year only one colony is starting to use it and my other 4 haven't touched it yet.
Then late February I add a pollen substitute patty and they always have this eaten by mid/late march. I make it from 2 parts soy flour to 1 part brewers yeast, mixed with just enough sugar syrup to bind it into a paste. Then squeeze between two pieces of greaseproof paper, about the size of an average burger and about 1 beespace thick so it sits under the crownboard.
So I keep the fondant and the pollen sub as two separate things, although the pollen sub does have a little sugar syrup in it.
People here will say this is waste of time because I have no scientific evidence but I do believe the colonies expand quicker in spring when using the pollen sub.