For the crust:
Preheat the oven to 350°F. Line an 8×8-inch baking pan with foil.
Arrange cubed Swirl Bread on a separate baking sheet and toast in oven for 5-6 minutes or until lightly browned. Using a food processor, pulse toasted bread into fine crumbs. Add sugar and salt and pulse once or twice to combine. Add the melted butter and pulse until the mixture is moistened.
Press the breadcrumb mixture into the bottom of the prepared baking pan. Bake for 15-20 minutes. Remove to a cooling rack and let cool completely. Increase oven temp to 375°F.
For the filling:
In a large bowl, use an electric mixer to beat all the sweet potato filling ingredients until well combined. Pour over breadcrumb crust and bake for 60 minutes, or until set but still slightly wiggly in the middle. Let cool to room temperature, then chill in fridge for 10-15 minutes to thicken slightly.
For the marshmallow topping:
In the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites and cream of tartar until soft peaks form.
Meanwhile, in a small saucepan set over medium-high heat, combine the sugar, corn syrup, water, and salt. Bring the mixture to a boil and continue to cook until a candy thermometer registers exactly 240°F. Immediately remove from heat. Turn the mixture on low speed and carefully and gradually drizzle the syrup into the egg whites. Increase speed to medium-high and beat until the mixture is thick and glossy and looks like marshmallow fluff, about 7 minutes longer. Add in vanilla and beat until combined.
Spread the marshmallow topping evenly over the sweet potato layer. Place the pan under the broiler and broil for about 1 minute, or until lightly golden.
Refrigerate pan for at least 1 hour before cutting into squares and serving.
Recipe adapted from: www.handletheheat.com