1tablespoonplus a teaspoon of vegetable oil18 grams
1large egg yolk
2slightly generous tablespoons sour cream38 grams
1/4teaspoonvanilla extractgenerous
3/4cupall-purpose flour3.4 oz
1teaspoonbaking powder
1/8teaspoonbaking soda
1/8teaspoonsalt
Nut Topping:
2tablespoonsbrown sugar
2teaspoonsflour
Pinchsaltomit if using salted butter
1/4teaspooncinnamon
2tablespoonschopped nuts
2teaspoonsunsalted buttermelted
Instructions
Preheat oven to 400 degrees F. and grease five muffins cups.
Mix together the mashed banana, sugar, vegetable oil and egg yolk. Stir in the sour cream and vanilla.
Mix together the flour, baking powder, baking soda and salt. By hand, stir flour mixture into banana mixture.
Scoop up batter and divide evenly among greased cups.
Make topping. Mix together brown sugar, flour, salt, and cinnamon. Stir in nuts. Add melted butter and stir until you have moist crumbs. Sprinkle tops of muffins with crumbs (you will have leftovers).
Bake on center rack at 400 degrees for 8 minutes.
Reduce oven heat to 350 degrees F and bake for another 15 minutes or until a cake tester or toothpick inserted in the muffins comes out clean. My muffins didn’t really seem done, but the toothpick came out free of crumbs so I knew they were.
Notes
You don't have to do this, but I've found that if I make the batter and let it stand for about 20 minutes before scooping, the muffins rise a little higher and have nicer crowns.