Thinly slice half of a large banana. Place on a small cutting board or baking sheet and place in the freezer until frozen, about 1-2 hours. This can be prepped in advance.
Add all ingredients to a blender: frozen banana slices, applesauce, soy milk, rolled oats, almond butter, cinnamon, maple syrup and ground flax seed. Blend on medium speed until smooth, about 1 minute.
Adjust maple syrup to taste and add extra milk as needed to reach desired consistency. Optionally, blend in 2-4 ice cubes for a colder smoothie. Serve topped with an extra dash of cinnamon.
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Notes
Bananas: Freeze sliced bananas in bulk for a quick smoothie ingredient. They keep for up to 3 months. If you're not a big fan of bananas in smoothies, choose a just-ripe banana instead of a super ripe banana.
Applesauce: I use individual cups of applesauce here but I keep them in the fridge so that the smoothie is colder.
Rolled oats: I recommend using rolled oats because they are more fiber-rich than instant oats, but instant or quick oats will work in a pinch.