For the dark butterscotch: Slowly melt together the chocolate and 6 tablespoons of the butter in a saucepan over low heat, whisking to completely combine.
Whisk together the brown sugar, sour cream, corn syrup, salt and eggs in a bowl, then add to the chocolate mixture. Cook, whisking continuously, until slightly thickened, then add the cornstarch and whisk continuously until thickened some more.
Remove from the heat and whisk in the remaining tablespoon butter until fully incorporated. Chill completely.
For the banana cream: Combine the banana, granulated sugar, cream, milk, flour and egg yolks in a blender and puree until smooth. Transfer to a saucepan and simmer for 2 to 3 minutes, until the mixture is slightly thickened, then whisk in the butter.
Transfer the mixture to a blender along with the bloomed gelatin and puree until smooth. Chill completely, then fold in the whipped cream.
For the cracked caramel dust: Grease a baking sheet with butter and set aside. Whisk together the granulated sugar, corn syrup and 1 tablespoon water in a small saucepan until completely incorporated. Simmer, covered, until the caramel is amber in color.
Uncover and continue to simmer until the caramel is just slightly smoking. Very carefully pour it out onto the prepared baking sheet. Crack when completely cooled.
For the slab vanilla shortbread: Preheat the oven to 350 degrees F.
Beat together the butter, confectioners' sugar and vanilla in a large bowl until creamy and smooth. Add the flour and salt and continue to beat until the dough just starts to come together.
Grease a quarter-sheet pan and press the dough evenly into the pan. Using a fork, poke a few rows of holes in the dough.
Bake until golden brown, 20 minutes. Cool completely.
To assemble: Fold the banana cream into the dark butterscotch and pour over the crust. Top with sliced bananas and sprinkle with the cracked caramel dust. Sprinkle with chocolate shavings and serve.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Slab Sandwiches and Pie, Seattle, WA