In a medium saucepan, on medium/high heat stir together the brown sugar, maple syrup and water.
Watch closely and stir occasionally.
Let mixture get to a light boil for 3 minutes.
Remove from heat.
Add the butter, walnut, Rice Krispies and salt.
Stir well.
Pour mixture onto a parchment lined cookie sheet.
Sprinkle with the sea salt.
Let cool.
Once cool, break up pieces.