
This Butterscotch Mousse Pie has a thick and chewy cookie crust made from walnuts, oatmeal, and brown butter. Its filled with rich, fluffy butterscotch mousse and topped with candied walnuts!
Place the butter in a small saucepan over medium heat. Allow it to melt and come to a gentle boil. Continue to cook it, stirring occasionally and scraping the bottom of the pan, as it grows darker in color. After about 6-8 minutes it should be golden brown and fragrant, with brown bits on the bottom. Remove the pan from the heat and pour the butter into a large mixing bowl. Let it cool to room temperature.
Line a baking sheet with foil and spray the foil with nonstick cooking spray. Combine the sugar and water in a small saucepan over medium-high heat. Stir until the sugar dissolves, then stop stirring. Bring the mixture to a boil and cook it, swirling the pan occasionally, until the sugar syrup is a medium amber and smells like caramelized sugar.
Combine the butterscotch chips, 3/4 cup of heavy cream, and salt in a medium saucepan. Place the pan over medium-low heat and warm up the chips, whisking frequently, until they’re entirely melted and the mixture is smooth. Pour the butterscotch mixture into a large bowl, and let it cool to room temperature, stirring occasionally.