• Preheat an oven to 350°F (177°C).

  Generously grease a 12-cup bundt pan with baking spray or brush it with vegetable shortening and dust it lightly with flour and set it aside.

Sift Together the Dry Ingredients and Combine the Liquids

• Into a 2-quart mixing bowl, sift together the cake flour, baking powder, ground cinnamon, baking soda, nutmeg, and ginger.

  Set this bowl aside.
• In a separate bowl or pitcher, combine the milk and mashed bananas.

  Set this aside for later.

  Toss the walnuts in 1 tablespoon (15 grams) of cake flour and set them aside.

Mix the Maple Walnut Banana Cake Batter

• Blend together the butter, brown sugar, and kosher in a 4-quart mixing bowl with your electric mixer set to low.

  Once the ingredients form a thick paste, stop the mixer and scrape down the bowl and beaters.
• Increase the mixer's speed to medium-high (or setting 4 on a Kitchenaid stand mixer) and beat the mixture for 4 minutes.

  Stop the mixer halfway through the mixing time to scrape down the bowl and beaters with a rubber spatula. 
• Add the eggs to the butter-sugar mixture, one at a time. Blend these in at low speed until they are incorporated into the mixture.

  Stop the mixer and scrape down the bowl and beaters after incorporating the final egg and the maple extract.

  Increase the mixing speed to medium-high and whip the mixture for 3 minutes. Stop the mixer halfway through the mixing time to scrape down the bowl and beaters again. 
• Add the banana-milk mixture to the bowl, alternating them with the dry ingredients, in two stages.

  Start with 1/3 of the dry mixture, follow that with 1/2 of the wet, and continue adding these ingredients, in these ratios, until all are incorporated into the batter.

  Mix each addition until they're no longer visible in the batter or for 30 seconds.
• Add the dusted walnuts to the bowl and use a rubber spatula to fold them into the batter until they are incorporated. 

Bake the Maple Walnut Banana Bundt Cake

• Scrape the maple banana walnut batter into the prepared bundt pan and give the pan a few taps on the countertop to expel any air bubbles.

  Place the cake pan into a preheated oven and bake the cake for 45 to 50 minutes, or until the cake begins to pull away from the sides of the pan. 

Brown the Butter for the Caramel Glaze (May Be Done 1 Day Ahead)

• Heat the butter in a 2-quart pot over medium-low heat for 4 to 5 minutes, stirring constantly, until you see brown flecks.

  When the butter emits a nutty aroma turn off the stove and remove the pot from the heat.

  Allow the butter to cool at room temperature until it solidifies or about 1 hour. 

Prepare the Caramel Glaze

• Add the brown sugar, whole milk, and salt to a 2-quart pot and stir them together for 2 to 3 minutes.

  Turn the stove up to medium-low after most of the sugar dissolves and use a wet pastry brush to brush the sides of the pot to remove any lingering sugar crystals.
• Cook the mixture until it reaches 210°F (99°C) on an instant-read thermometer or a candy thermometer.

  Remove the pot of caramel from the stove and allow it to cool at room temperature for 15 minutes.

  After 15 minutes, scrape the caramel into a 2-quart mixing bowl and allow it to cool completely.
• Once the caramel cools to room temperature, add the solidified browned butter and maple extract.

  Use an electric mixer to blend these ingredients until they form a thick glaze that's the consistency of molasses. 

Cool, then Glaze the Maple Walnut Banana Bundt Cake with the Brown Butter Caramel Glaze

• Remove the bundt pan from the oven once it's done baking and allow the cake to cook in the pan for 5 minutes.

  After 5 minutes, turn the cake onto a cooling rack to cool completely.
• To decorate your maple walnut banana cake, pour as much or as little of the brown butter caramel glaze over its surface.

  Garnish with chopped walnuts, or serve it as is.