If you’ve never tried sweet potato in a smoothie before, you’re in for a treat. They add a nice creamy texture as well as some sweetness and subtle flavor. In some ways it evokes the pumpkin in the pumpkin pie smoothie, and you can substitute sweet potato for the pumpkin in that recipe.
There are two main types of sweet potatoes, and I go for the soft/moist/orange type, as opposed to the lighter colored dry type. I usually find Garnet or Beauregard varieties, but there are others that are interesting to try as well. There’s sometimes confusion* because these orange sweet potatoes are often sold as yams in the US. Technically they’re not actually yams, which are larger and are generally not available in the US, but they’re called yams here for historical reasons.
I like to bake the sweet potatoes when I get back from shopping, and then store them in the fridge for the week. I wash and scrub them with a vegetable brush, and then put them into the preheated oven. Lately I’ve been putting them directly onto an oven rack, and then putting a foil-covered cookie sheet on the rack directly below them to catch the drips, which will otherwise burn onto the bottom of your oven. I bake at 400 °F for 45-60 minutes depending on size, until they are soft (if you have kitchen tongs they work well for a quick squeeze test). Alternatively, you could steam or boil them, but I haven’t been doing that.
The skins are fine to leave on for smoothies in your high-powered blender. In this recipe I paired the sweet potato with cranberries (frozen are fine) and ginger, and then added an apple and some soaked walnuts to round it out. Other nuts would also work fine.
This was a single large serving. Blend on high until smooth and enjoy.
*The question of yams vs. sweet potatoes confused me when I was looking for sweet potatoes to use in a recipe a few years ago. I was getting ready to make Bittman’s sweet potato salad, but at the grocery store the sweet potatoes that are like the ones he uses (and the ones I recommend for smoothies) are sold as yams. That first time to be on the safe side I got both kinds of sweet potatoes, but I later confirmed that the ones he uses are the ones I saw labeled as yams.
Update: For a different flavor, skip the cranberries and add some cinnamon—you’ll end up with a flavor that’s like a cross between apple and sweet potato pie. If you find them, you can have fun with purple sweet potatoes.