Add all the ingredients to food processor/blender minus walnuts and blend until smooth. Stir in walnuts, if using. Let batter sit for 10 minutes.
Heat a pan or griddle over medium to medium-low heat. Coat pan with butter or oil. Drop 1-2 tablespoons of batter into the pan. Cook until bubbles start to form and the edges of the pancake begin to appear solid(about 3 minutes). Carefully flip. Cook for another 2-3 minutes.
Serve as is or with topping of choice (see note)
If the bottoms start to brown too much before they are set, lower the heat.
Allow to cool COMPLETELY. The pancakes will firm up beautifully as it cools. I've also noticed that the yogurt flavor becomes more mellow as it sits.
If you desire a sweeter pancake, do NOT add more applesauce. What I learned is that the unsweetened applesauce + Greek yogurt make the pancakes quite tart. Instead, add 1/2 medium banana, mashed.
Store in an airtight container for 3-4 days in the fridge. Warm slightly before serving (no more than 15 seconds in the microwave). Store in the freezer for up to 3 months.