For those who might be interested, I've managed a few more variables in my
quest for the ultimate breakfast drink.

My standard recipe is 1.5 to 2 cups of Belsoy soy milk (about 2 carbs/cup)
with a scoop of low carb powder mix (e.g. Zero Carb IsoPure) mixed in the
blender. Variations include substituting some of the soy milk with whipping
cream (yum!).

The latest experiment was the inclusion of tofu. I found that regular tofu
was kinda yucky, but the soft silken tofu thickens the drink nicely. I use a
quarter package, blend it on low speed, and slowly add the milk.

The other, less successful, experiments included agar gum and psyllium husk
to thicken the concoction. I already knew psyllium husk flakes wouldn't
work, but I hoped the powder version would. The agar gum and the powdered
husk settled to the bottom and didn't do much to thicken the drink.

I've also tried adding plain protein powder and good tasting yeast to the
drink. This was successful but I'm unsure of the carbs. Cottage cheese,
yoghurt and sour cream have all made their way into the blender, but the
taste could not justify the carb count.

The inclusion of Davinci syrups is, of course, to your taste. I've picked up
a few and found that the fruity syrups work well, as does the chocolate.

If you've got some variations on your drink, please let me know!