Preheat oven to 375° F. Spray a muffin tin with cooking spray and/or line the tin with cupcake liners. (See Cooking Notes below for tips about the tin.)
To a large high-powered blender, add the oats and blend until fairly smooth. Then, add the rest of the ingredients to the blender and secure the lid. Start blending on low and increase speed until the wet ingredients are well blended and batter is smooth and creamy. You will have to stop and stir a few times, scraping down the sides.
Pour or scoop the batter into the muffin tin, filling each cup until almost full (about a heaping 1/4th cup of batter per muffin.) Sprinkle a pinch of rolled oats or mini chocolate chips on top of each muffin, if desired. If you really scrape out as much batter as you can, you'll end up with 15 muffins.
Bake for 15-18 minutes, until the tops of your muffins are set and a toothpick inserted into the middle comes out pretty clean (you may see just a few crumbs on the toothpick). Note that silicone pans may require about 5 minutes more of bake time.
Allow muffins to cool in pan for about 10 minutes before removing to a cooling rack. They are delicious warm and with a little butter on them. Once they are fully cooled, store in an air-tight container for up to a week in the fridge or freeze using directions below.
Freeze For Later: Bake muffins as directed in recipe. Let cool completely. Once cool, place muffins in freezer safe bag or container, squeeze out as much air as possible, and seal tightly. Freeze for up to 3 months.
Prepare From Frozen: Thaw desired amount of muffins overnight in the refrigerator or warm them slightly in the microwave.