Position racks to divide oven in thirds and preheat oven to 325 degrees F. Lightly coat 21/2-inch muffin cups of one or two muffin pans with nonstick cooking spray.
In a very large bowl toss together the puffed rice, peanuts, puffed whole grain, dried fruit (if desired), sesame seeds, and the salt.
In a small saucepan bring rice syrup just to a boil over low heat (or boil in a microwave). Remove syrup from heat; let stand for 2 minutes. Add miso and both oils; whisk to blend. (It's OK if the miso doesn't dissolve completely, leaving little strands.)
Pour the warm liquid over the dry ingredients. Using a silicone spatula, stir for a few minutes until all is moistened. Fill each muffin cup with 2 Tbsp. of the mixture; press flat with the bottom of a jar. Bake for 15 to 18 minutes (rotate the muffin pans front to back after 8 minutes) or until cookies are golden brown. Transfer to wire racks and cool completely before unmolding.