I use EZ-Sweetz, which is a super-concentrated liquid Splenda. The granular Splenda has fillers in it, and the fillers have carbs. Liquid sucralose has no carbs.
For chocolate desserts, I find it best to use a mix of sweeteners. Lately I've been using Truvia and the EZ-Sweetz together, which gives pretty good results. I just bought some powdered erythritol, which is supposed to be the sugar alcohol with the least effect on BG.