It will look like this.
Add eggs, one at a time, beating well after each egg. In yet another bowl, mash up your banana. I use frozen bananas. Whenever I have banana on the counter that starts getting too brown for the people in my family to eat, I toss it in the freezer. Frozen bananas are great for baking. And for making baby food (sidebar- I made all of the food that both of my babies ate. Neither ever ate a jar of food, at least not from my hands! I didn't set out that way but it ended up being so stinkin' easy that I just kept going with it and suddenly... no more purees, just table food. I think making my own baby food made the transition to table food easier.).
Add your milk and vanilla to the mashed banana.
" With mixer on low, alternately add flour mixture and banana mixture to butter mixture, beginning and ending with flour mixture; mix just until combined. "
I forgot to take a picture of the frozen blueberries in the batter. Or even of the batter after all of that alternating of flour and banana mash... so skip right ahead to...
Fold blueberries into batter. (Fold them because they are delicate and if you just stir them, the berries and juices will just take over the batter and everything will be bluish-purple. If you don't know how to "fold," think of it like laying the blueberries on top in a strip and then tucking them into bed for the night. You just ease batter up and over, up and over and the blueberries will incorporate into the batter gently.)
Fill up those muffin cups! The recipe makes 12 so fill them pretty full.
"Bake until a toothpick inserted in the center of a muffin comes out clean, 25 to 28 minutes, rotating pan halfway through. Let cool in pan 10 minutes; transfer muffins to a rack to cool 10 minutes more. "