Pour 1 cup of whole milk and 1 tablespoon of salted butter into a small saucepan and heat over medium heat for 3 to 4 minutes, stirring occasionally, until the butter melts and steam wisps appear; do not boil.

Stir in 1/4 cup of butterscotch syrup into the hot milk and whisk until fully incorporated and smooth.

If using, add 2 ounces of butterscotch schnapps to the milk mixture and stir well to combine.

Divide 2 cups of cream soda between two tall glasses, pouring 1 cup into each glass.

Slowly pour the hot butterscotch milk mixture into each glass of cream soda, stirring gently once or twice to blend without losing carbonation.

In a clean bowl, combine 1/2 cup of heavy cream, 1 tablespoon of brown sugar, 1/4 teaspoon of vanilla extract, and a pinch of salt; whip with a whisk or handheld mixer for 2 to 3 minutes until soft peaks form.

Spoon a generous dollop of the whipped cream topping onto each glass, letting it sit slightly above the rim.

Drizzle a light amount of butterscotch syrup over the whipped cream and serve immediately while warm.