Preheat oven to 350°F. Line muffin cups with paper liners.
In a mixing bowl, whisk together vegetable oil, butter, vanilla, brown sugar, egg, and yogurt.
Mash the banana and stir into the mixture; add chopped nuts.
Stir in flour, baking powder, baking soda and sea salt. To avoid tough and dry muffins, do not overmix batter.
Fill muffins cups 2/3 full or about 1/2 cup of batter.
Bake in preheated oven for 23 to 25 minutes, or until muffin tops are golden brown. Be careful to avoid baking muffins too long or they will be dry.
Remove from oven and cool on a wire rack.