Line an 8x8 inch pan with parchment paper.
In a large pot, on medium low heat, melt the peanut butter, maple syrup, coconut oil, and salt until smooth, then stir in vanilla. Turn off heat.
Mix the cornflakes with the peanut butter mixture until coated. Press firmly into the pan and freeze for 10-15 minutes.
Melt the chocolate, peanut butter and coconut oil together, then spread over the base. Top with sea salt if desired.
Refrigerate for 1 hour, then slice.
