Salted Butterscotch Mousse Cups

Put the egg whites in a small, very clean bowl, cover, and refrigerate. Put the yolks in a medium bowl and add the cornstarch, vanilla, and 1/2 cup of the milk. Whisk well. Set aside.

In a medium saucepan, melt the butter over medium heat. Add the brown sugar and salt and stir with a whisk. Add the remaining 2 1/2 cups of milk to the pan and whisk until smooth. Turn the heat up to medium-high and cook, whisking regularly, until the milk heats up and tiny bubbles form around the edge. When the milk looks like it’s just about to boil, turn it down to low so that it doesn’t, and scoop 1 cup of milk from the pot.

Very slowly pour the cup of hot milk into the bowl with the egg yolks, whisking the entire time so the heat of the milk doesn't scramble the eggs. Then, slowly add the milk/egg mixture to the pan with brown sugar/milk, whisking all the while. Turn the heat to high and bring the pudding to a boil, whisking continuously. Cook until the pudding turns thick and creamy. When it is thick enough that a line forms when you drag a spoon through the center, the pudding is done. Remove from heat. Transfer to a medium bowl and cover the surface with a piece of plastic wrap so that it doesn't form a “skin”. Refrigerate until the pudding is completely chilled and firm, several hours or overnight.

Remove the pudding from the refrigerator and stir with a whisk until creamy.

Put the egg whites into the bowl of an electric mixer, making sure your equipment is supremely clean. Whip the egg whites on medium-low speed. After about 1 minute, when the whites begin to foam, add the cream of tartar and continue to beat, gradually increasing to high. When the whites begin to thicken, add the sugar and continue to whip into stiff peaks, keeping in mind that pasteurized whites take longer than non-pasteurized, so be patient.

Add the whipped egg whites to the pudding and use a rubber spatula to gently fold them in until you have a creamy, smooth mousse. Add 1 tablespoon of the chocolate sauce to the bowl and run a spoon through it to make chocolate ribbons in the mousse.

Divide the butterscotch mousse between 8 small bowls, glasses, or jelly jars. Top each one with a tiny sprinkle of fleur de sel, if using. Peel and cut the bananas into thin slices and divide them over the pudding. Top each one with a small drizzle of the remaining chocolate syrup. Serve immediately.