Add the brown sugar, corn syrup, butter, and cinnamon to a medium saucepan. Cook over medium heat, stirring occasionally, until the mixture is smooth.

Slowly pour in the heavy cream while stirring constantly. Once combined, bring the mixture to a boil and continue cooking for 1 minute.

Transfer the butterscotch to a heatproof container and let it cool at room temperature for 30 minutes. Refrigerate until completely chilled before using.

Prepare the pie crust according to the package directions. Let it cool completely, then break it into small, bite-sized pieces. Avoid making the pieces too fine because you want distinct pockets of pastry throughout the ice cream.

Add the heavy cream and vanilla to a large bowl and beat with an electric mixer until stiff peaks form. Be careful not to overbeat the cream once it reaches stiff peaks because it will get grainy.

Add the sweetened condensed milk, cinnamon, and salt. Gently fold everything together with a rubber spatula until smooth and evenly combined, being careful not to deflate the whipped cream.

Pour the ice cream mixture into a large freezer-safe container, filling halfway. Spoon or drizzle chilled butterscotch over the surface, then scatter pie crust pieces on top. Repeat with the remaining ice cream, butterscotch, and pie crust.

Swirl the layers together with a butter knife. Don't overmix! The goal is to create ribbons of butterscotch rather than fully mixing it into the ice cream.

Cover tightly and freeze for at least 8 hours, preferably overnight, until firm. Let the ice cream sit at room temperature for 10-15 minutes before scooping.