• Preheat the oven to 350º. Butter a 9 x 13 baking pan.

Cake:

• In a medium bowl, whisk the flour, baking powder, and salt.
• In a 2 cup measuring cup or microwave safe bowl, melt butter and let it cool. Add oil and whisk together.
• Wipe down the inside of a mixing bowl with lemon juice, then dry it with a paper towel. Add egg whites and beat on medium speed until light and frothy, about 2 minutes. Turn to medium-high and gradually add the sugar a little at a time. Once added beat on high until shiny and stiff peaks have formed, about 3 minutes. Add vanilla and beat to combine.
• Gently fold the flour mixture into the egg whites, then fold in the butter mixture. Pour into the prepared pan and smooth out the top. Bake for 23-25 minutes until it is slightly brown and a toothpick comes out clean. Let cool completely on a wire rack.

Pudding:

• In a saucepan, whisk together the milk, cream, cornstarch, eggs, egg yolks, sugar, vanilla and salt. Heat over medium heat, whisking constantly until has thickened, about 8 minutes. It should be pretty thick but it will continue to thicken as it cools. Remove from the heat and whisk in butter. Pour it into a glass bowl and press plastic wrap directly on the surface. Cool to room temperature, about an hour, then refrigerate for at least 1 hour or up to 2 days.

Whipped topping:

• When ready to assemble, beat the cream until slightly thickened then add the sugar and vanilla and beat until stiff peaks form, about 2-3 minutes.

Assemble:

• Use the end of a wooden spoon to place holes in the cake. Use a spatula to gently push the pudding into the holes then cover the cake with the remaining pudding. Top with a single layer of sliced bananas. Cover with whipped cream and top with vanilla wafers. Cover with plastic wrap and refrigerate for at least 1 hour.