• Preheat oven to 375℉.
• Line a 12 cup muffin tin with cupcake liners. Set aside.

Make the Streusel Topping

• Melt the butter for the streusel topping over low heat in a small saucepan.
• Stir in the brown sugar, cinnamon and salt.
• Stir in the flour and oats. The mixture should come together and form some small clumps. Remove from heat.

Make the Muffin Batter

• In a medium bowl, whisk together the flour, salt, baking powder and baking soda. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and brown sugar on medium speed.
• To the stand mixer, add the bananas and mix until they are mashed and well incorporated.
• Add the sourdough starter, egg and vanilla and continue to mix until fully combined.
• With the stand mixer set to low speed, slowly add the flour mixture. Mix until almost fully combined.
• Turn off the stand mixer and stir in the pecans or chocolate chips by hand with a wooden spoon or rubber spatula.
• Divide the batter across the prepared muffin liners. Top the muffins with streusel topping.
• Bake in preheated oven for 23-25 minutes or until a toothpick inserted into the center of a muffin comes out clean.