Splenda® (the American brand name for sucralose) says on the box that it "can be used to replace sugar in most of your favorite recipes." The key word here is "most."
We tried making brownies from a basic recipe almost identical to this one but substituting a cup of Splenda® for the sugar. When we pulled the pan from the oven, the brownies themselves were very flat and surrounded by a bubbling white foam. We poured off the foam and let the brownies cool. They tasted something like chocolate-flavored dog biscuits.
Although I've been using the plural pronoun "we," in reality only one of us had made the brownies, and the other of us hadn't been in the kitchen at the time, so there was an uncomfortable and unvocalized question hanging in the air, namely "Are you positively sure you didn't leave out an ingredient?" I mean, these brownies were so wrong that there had to be a major mistake involved. Yet, some egg shells were in the garbage, and some butter was missing, and flour still speckled the counter top.
So we tried again, the two of us together, and this time we checked and double checked each step in the sacred brownie-making ritual. When we removed the second batch from the oven, they were again covered with a bubbling white foam, but we didn't pour it off this time, thinking that perhaps it would be reabsorbed and the brownies would expand to their full chewy dimensions.
That actually happened to a certain extent. This second batch was a little plumper and a little moister, but they actually tasted much worse.
So for now we've given up on trying to make brownies with Splenda®. Perhaps some foods are so perfect they will tolerate no substitutions. Never tamper with genius. On the other hand, this afternoon Deirdre made some peanut-butter cookies and some gingerbread cookies with recipes from the Splenda® web site and they turned out truly glorious. The holidays are saved!