In a medium saucepan over medium heat, combine honey (or corn syrup) and brown sugar. Stir constantly until the sugar dissolves and the mixture just begins to bubble.

Remove the pan from heat and immediately stir in the peanut butter and vanilla extract until the mixture is smooth and creamy.

Pour the Rice Krispies into the warm peanut butter mixture and stir gently until all the cereal is fully coated.

Lightly grease or line a mini muffin tin. Spoon the mixture into each cup, pressing down gently with a greased spoon or your fingers to compact it.

In a microwave-safe bowl, combine the chocolate chips and 2 tablespoons peanut butter. Microwave in 30-second intervals, stirring in between, until smooth and melted.

Spoon the melted chocolate mixture over the Rice Krispie cups and smooth out the tops. Sprinkle with mini chocolate chips or flaky sea salt if desired.

Refrigerate for at least 30 minutes until fully set. Once chilled, pop the cups out of the muffin tin and store them in an airtight container.