Prepare the butter and wonton wrappers: In a small bowl, add butter, pineapple juice, brown sugar and a pinch of salt. Zap for 30 seconds. Add wonton wrappers into melted butter mixture.
Fill the mugs: Toss walnuts and chocolate chips in a bowl. Divide the bananas into 6 portions. In the bottom of two 12-ounce mugs (1 1/2 cups capacity), add 1 portion of the bananas. To both mugs, add a pinch of the walnut and chocolate chip mixture; then pour over a spoonful of the melted butter mixture and layer on a wonton wrapper. Repeat the layers, with the last third of bananas in each mug, topped by the last third of walnuts and chocolate chips and the remaining melted butter mixture.