• Preheat the oven to 350 degrees F. Grease an 8-by-8-inch square baking pan and line with a sheet of parchment paper so that the parchment paper has extra flaps coming off all of the sides. This way you’ll be able to lift the cake out of the pan. Just makes sure it’s about 3-inches up the sides because this guy rises a bit.

To Make the Walnut Streusel:

• In a bowl, combine the sugar, flour, walnuts, cinnamon, nutmeg, kosher salt, and butter and mix together. Use your fingers to press the butter into the mixture until it’s about pea shaped. Pop the bowl into the fridge to chill.

To Make the Espresso Filling:

• In a small bowl, combine the brown sugar, instant espresso, cinnamon, and kosher salt and mix until well combined. Set aside.

To Make the Coffee Cake:

• In a bowl, whisk the flour, sugar, baking powder, baking soda, cinnamon, nutmeg, and kosher salt together.
• In a large bowl, whisk the mashed banana, sour cream, oil, melted butter, eggs, and vanilla extract until well combined. Add the flour mixture and mix together with a spatula or wooden spoon until just combined; don’t overmix as it will yield a tougher crumb.
• Add a little more than half of the batter to the bottom of the lined baking pan and smooth with an offset spatula. Evenly sprinkle the filling over the smoothed batter and cover with the remaining batter. Gently smooth the batter with the offset spatula.
• Remove the streusel from the refrigerator and evenly sprinkle it over the cake. Bake for 45 to 50 minutes or until a skewer comes out clean when inserted into the center. Cool the cake in the pan set on a cooling rack.

To Make the Maple Glaze:

• In a small bowl, combine the powdered sugar and maple syrup until smooth. Then, drizzle the glaze over the banana bread coffee cake. Allow the glaze to set for a few minutes then cut into 9 pieces and enjoy! Store any extra coffee cake in an airtight container to keep at room temperature (for up to three days).