In a large bowl, stir oats, rice cereal, and walnuts together, set aside.
In a medium saucepot, melt the butter, honey, and brown sugar together until it comes to a bubble. Reduce the heat then cook for 2 minutes more.
Add vanilla to the saucepot and stir.
Pour the mixture over the dry ingredients and mix together until just moistened.
Pour onto prepared baking sheet and press out to about 3/4 inch thick - if your sheet is too big, you can press them all to one half of the baking sheet to make them thicker. Sprinkle with mini chocolate chips and press them down lightly. Let cool on countertop until room temperature or for 2 hours, then cut into bars.