Batter Preparation: In a medium sized bowl, combine egg yolks and sugar. Whisk together until it turns a pale yellow color. Cut vanilla beans lengthwise and scrape out the seeds. Add seeds to yolk mixture. Add the cream and mix until completely incorporated. Add vanilla pods, and let sit.
Salted Caramel Preparation: Pour the sugar in an even layer into a heavy saucepan. Turn heat to medium and let sugar cook, whisking intermittently until it starts to melt. Once melted, whisk constantly until it reaches a nice amber color. Using a candy thermometer, check the temperature – once the sugar reaches 350 degrees, carefully add all of the butter. The sugar will bubble, this is normal. Whisk until the butter is fully incorporated then remove from heat. Slowly add the heavy cream, whisking constantly until fully incorporated. Whisk in the salt. Sauce can be stored up to 2 weeks in the fridge.
Assembly: Remove vanilla pods from the batter mixture and discard. Cut the bananas on a bias. Lay out the bread slices. Drizzle caramel sauce over bread. Top 4 pieces with bananas and toffee chips. Use the remaining 4 slices to top the bananas, caramel side down. Set the “sandwiches” in the batter mixture for 20-30 seconds on each side.
Cooking: Melt butter in a large skillet on medium heat. Toast “sandwiches” until golden brown on each side.
Plating: Cut the “sandwiches” diagonally, and drizzle with remaining caramel and top with toffee chips. Pairs nicely with whipped cream.