Add cereal to a large mixing bowl. Pour over melted chocolate and toss well to coat. Spread onto a parchment-lined baking sheet. Let set for 10-15 minutes in the fridge. Break into clusters and set aside. 

In a large mixing bowl, whisk together butter, sugars, yogurt, cocoa powder, and milk until creamy. Add flour, baking soda, and salt. Use a wooden spoon or silicone spatula to fold dry ingredient into wet until a soft dough forms. Fold in 1/2 of the cereal clusters and all of the chopped chocolate. Chill dough for at least 30 minutes (ideally overnight).

Preheat oven to 350°F. Use a 1.5-2 tbsp cookie scoop to distribute dough onto parchment-lined baking sheet. Top with remaining cereal clusters. 

Bake for 12 minutes. (Optional): To create perfectly round cookies, place a mug/glass or circular cookie cutter over the warm dough and do a little swirl to form a round cookie. Allow cooling on the baking sheet for 10 minutes before transferring to a wire cooling rack. (Optional): drizzle over simple icing and flaky sea salt.