Oil a 9x13 inch metal or glass baking pan with 2 inch sides. Reserve
In a medium skillet over medium high heat, swirl the oats until they are fragrant and toasted, about 3 minutes. Transfer to a large bowl so that they will not burn. Add the crispy rice and salt and stir to mix.
In a small saucepan, combine the rice syrup and brown or palm sugar. Over high heat, bring to a boil, then reduce to a low bubble for one minute. Take off the heat and stir in the peanut butter and vanilla until smooth. Pour over the oat mixture and mix well.
Scrape into the prepared pan and use wet hands to press evenly in the pan.
Chill for at least 3 hours before removing from the pan. Get a cutting board, and use a metal spatula to go around the edge of the pan, loosening the bars. Place the cutting board on top of the pan and invert. The bars should drop out, tap the bottom of the pan if needed to get them to drop.Melt the chocolate and spread over the bars. If desired, you can sprinkle with chopped peanuts.
Chill the pan until the chocolate is set.
Slice into four even squares, then slice each of those into four bars. Store in an airtight wrapper or container in the refrigerator for up to two weeks.