Preheat the oven to 325 degrees F.
Spray the inside of an angel food cake pan (easier to use) or fluted Bundt pan with nonstick spray. Lightly dust with sugar and set aside.
In a stand mixer fitted with the paddle attachment, cream the butter with the sugars until light and fluffy. Add the eggs, one at a time, mixing each one in completely before adding the next. Add the mashed banana and the vanilla and lemon extracts, and beat until completely incorporated.
Add a third of the flour to the wet mixture, beating it in completely. Then add a third of the sour cream, beating that in completely. Continue to alternate flour and sour cream until all of it is incorporated. Beat in the salt, then pour the batter into the prepared pan. Bake for 70 to 90 minutes, or until a cake tester comes out clean. Let the cake cool for 5 minutes. Use a small metal spatula to carefully release the cake from the pan. Unmold the cake and let cool before slicing.
For the chocolate sauce: Combine the cream, honey, brown sugar, cocoa powder and 1 cup of the chocolate chips in a saucepot over medium-high heat. Bring to a boil, then add the salt and cook, stirring occasionally, until the sauce becomes completely smooth, 5 to 10 minutes.
Off the heat, stir in the remaining 1 cup chocolate chips and the butter. Transfer to a jar and set aside until ready to serve.
To serve: Preheat a grill or grill pan to medium high. Brush slices of the cake with some melted butter, and grill just until light grill marks appear, 1 to 2 minutes. Remove to a serving platter. Drizzle with chocolate sauce and enjoy.