Preheat your oven to 350°F. Line an 8-inch square tin with baking paper, then spray with non-stick cooking spray or oil.
In a medium bowl, combine the coconut, vanilla, salt and egg whites. Stir in the chopped white chocolate and sugar. Press into the lined tin.
1.5 cups desiccated coconut, 1 tsp vanilla extract, 1/8 tsp salt, 2 egg whites, 1/3 cup granulated sugar, 1/3 cup white chocolate
Wrap the bananas in foil. Place the foil-wrapped bananas and the coconut base into the oven. Bake for 25-30 minutes until the coconut base is golden brown and the bananas are dark and starting to seep a bit.
2 medium bananas, mashed
Immediately peel the bananas into a bowl and mash roughly with a fork.
Spread the mashed banana over the coconut base and sprinkle on the chopped chocolate. Spread the chocolate evenly to cover the entire base and sprinkle with marshmallows.
4 ounces dark chocolate, 2 cups mini marshmallows
Turn your broiler on and put the oven rack on the top third of the oven. Place the pan under the broiler for less than one minute, just until the marshmallows are toasted. Watch them closely!
Allow to cool completely (popping them into teh fridge helps) then remove from the pan and peel away the baking paper.
Cut into 12 or 16 squares.