Preheat oven to 350℉.
Add buckwheat flour, whole wheat pastry flour, baking soda and coconut sugar to a small mixing bowl. Whisk to combine evenly.
Add miso, vanilla, peanut butter, extra virgin olive oil, whole egg, and egg yolks to a medium mixing bowl and beat on medium speed until blended. Add dry ingredients to this and beat on low until combined, stopping occasionally to scrape sides and bottom of bowl with spatula.
Add chocolate chunks and fold in with spatula or wooden spoon.
Divide batter evenly (about 2 ounces each) into 8 mini cast iron skillets (3.5” diameter). Sprinkle tops with chopped cashews and sesame seeds. (See link in notes below for mini skillets.)
Bake for 8-12 minutes until puffed with set but soft centers. These are best served warm and freshly-baked.