Preheat oven to 350 °F (177 °C). Line muffin tins with baking cups, set aside.
In a medium bowl, whisk together flour, baking soda, cinnamon, and salt.
In the bowl of a stand mixer fitted with the paddle attachment, cream together butter and brown sugar until creamy and fluffy. Add in the bananas, eggs, and vanilla extract. Beat well until incorporated.
Slowly add in the dry ingredients until just combined. Spoon batter evenly into prepared muffin tins.
In a small bowl, combine all streusel ingredients except the toffee bits. Mix well then stir in toffee bits.
Generously spoon streusel mixture all over the tops of the muffin batter.
Bake for 18-25 minutes or until light golden brown. Let stand for 5 minutes before removing muffins from pan. Let cool completely on a wire rack.