Not surprisingly the kids preferred the energy dense soups.
Perhaps slightly surprisingly, how much the kids liked their soups from the get go didn't impact on how well they liked the non-spiked soups 6 months later. At that point all that mattered was exposure.
As I've mentioned in the past, my house is part of the "one bite to be polite" community and we've found that over time those bites condition our girls' palates to a wide variety of tastes and foods, while the one bite to be polite prevents those exposures from turning new flavours into battlegrounds.
[And please don't read this post as stating that I'm averse to you putting butter on veggies - that's quite delicious - I just used the study to illustrate the point that exposure is king]