Preheat oven to 350 degrees
Start with the streusel topping. Mix cooled melted butter, brown sugar, sugar, cinnamon, salt and flour in a bowl using a fork. It will resemble wet sand and will clump together. Place in the freezer while you work on the cake.
To a bowl mash 4 ripe bananas with a fork. Set aside.
In a separate bowl sift together flour, salt, cinnamon and baking powder. Set aside.
To a stand mixer or with a handheld mixer beat softened butter, sugar and maple syrup together for one minute.
Add the eggs, vanilla and mashed bananas and beat until combined.
With the mixer on low alternate adding the dry ingredients and the half & half to the wet ingredients until you're out of both.
Mix until everything is well combined. Scrape the bowl down and mix again.
Remove the streusel topping from the freezer and break it up with a fork. You want varying sizes of crumb.
Line a 9x9 pan with parchment paper.
Pour half the batter in the bottom of the pan and spread out. Cover with half of the streusel mixture. Cover that with the rest of the batter and carefully spread out. Top with the rest of the streusel topping.
Bake uncovered in the middle rack for 50 minutes.
Cool completely before cutting. Best served at room temperature.