I've made this twice today and both times it came out too sloppy/wet to use at room temperature. I used: 2 egg whites 1/2 c sugar 1 stick of butter lemon zest Whisked the egg whites and sugar in a double boiler until I couldn't feel the grains of sugar anymore. Put it in the mixer and beat it until it was glossy/fluffy/forming stiff peaks and the bowl was room temperature to the touch, 8-10 minutes. Added the room temp butter a bit at a time. mixing well after each addition. Folded in the lemon zest. The first time I used the paddle attachment. The second time I used the whisk until after all the butter was incorporated, then switched to the paddle to get rid of any air bubbles. (Martha Stewart says so!) If anything, the second batch was looser than the first. The first one firmed up in the fridge but then never got soft enough again to spread easily. The second batch is cooling in the fridge right now because it's way too loose to spread on the cake at room temp. Is there a way to save this?