Preheat the oven to 350°F (175°C). Lightly spray a 12-cup muffin tin or line it with muffin liners.
In a blender, add the eggs, ⅓ cup milk, 1 teaspoon vanilla extract, ½ cup creamy peanut butter (sugar free), and the 2 medium ripe bananas. If using the ¼ cup golden monk fruit sweetener, add it now.
Add the dry ingredients to the blender: 2 ¼ cups old fashioned oats, 1 ½ teaspoons baking powder, ½ teaspoon baking soda, ¼ teaspoon salt, and, if using, ½ teaspoon cinnamon.
Pulse the blender until the oats are ground and the batter is smooth and uniform.
Pour the batter into a mixing bowl. Set aside some of the ½ cup sugar free chocolate chips for topping, then fold the remaining chocolate chips into the batter.
Divide the batter evenly among the 12 prepared muffin cups. Top each muffin with the reserved chocolate chips.
Bake for 15–20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and carefully transfer them to a cooling rack to cool.