Line an 8x8-inch baking pan with parchment paper, leaving an overhang on two ends for easy removal.n2. In a microwave-safe bowl, melt the mini marshmallows, peanut butter, and butter together for about 30 seconds to 1 minute until smooth, stirring occasionally.n3. Stir in the vanilla extract until combined.n4. Add the Rice Krispies cereal and mix well until fully coated. For added texture, mix in the brown rice syrup.n5. Pour the mixture into the prepared baking pan and press down evenly with a spatula or your hands.n6. Let the treats set at room temperature for about 30 minutes until firm, then cut into bars and enjoy!