Line a 9-inch x 9-inch square pan with parchment paper. Lightly oil the paper with cooking spray or coconut oil. Set aside.
In a medium-size saucepan, add fresh runny peanut butter, maple syrup, coconut oil, salt, and vanilla. Bring under low/medium heat, stir and cook until it melts and comes together into a thick creamy paste. It takes just 1 minute, don't overcook it, or it sticks to the pan. You can also microwave the mixture in a microwave-safe bowl by 30 seconds burst, stir between each session in the microwave, until creamy.
Place the rice crispy cereals into a large mixing bowl (start with 2 cups + 1/2 cups) and pour the peanut butter mixture on top.
Combine with a spoon until all the cereals are coated. If you used small puffed cereals, you might want to add 1/2 cup puffed cereals, adjust to taste.
Pour the mixture into the prepared pan. First, spread evenly with a greased spatula. Then, lay a piece of parchment paper on top of the bar to fully cover the bar. Next, press/rub the surface hard enough to compact the bar and avoid air between rice crispies (see picture above in the post for tips).
Place the pan in the freezer to set, about 10-15 minutes, meanwhile prepare the chocolate layer.
In a small saucepan, over low-medium heat, melt dark chocolate chips, coconut oil, and peanut butter until smooth and shiny.
Remove the pan from the freezer and pour the melted chocolate all over the bar.
Spread the chocolate using a greased spatula until all the bar is coated with the melted chocolate
Return the pan to the freezer for 10 minutes or until the chocolate layer is set. Then, refrigerate for 1 hour before slicing.
Remove from the fridge and wait for 5 minutes before cutting to prevent the chocolate top layer from cracking.
If you can, warm the blade of your knife under a flame or boiling water (dry in a towel) and cut the bars into 12 squares. The warm blade will cut the chocolate layer easily, preventing the layer from breaking into pieces.
Store in the fridge for up to 2 weeks. The cereals soften slightly after 1 week, and that's normal.