Preheat your oven to 350°F (175°C).
Grease your 9x9-inch baking pan or line it with parchment paper.
In a large mixing bowl, whisk together the melted butter and granulated sugar until combined. Add the eggs one at a time, mixing thoroughly after each addition, then stir in the vanilla extract.
In another bowl, sift together the all-purpose flour, cocoa powder, espresso powder, salt, and baking soda.
Gradually add the dry mixture to the wet mixture, stirring gently until just combined.
Fold in the melted and cooled Nutella until well incorporated, then mix in the chocolate chips.
Add the crisped rice cereal and fold it into the batter.
Pour the batter into the prepared baking pan and spread it out evenly. Bake for 25-30 minutes.
Once baked, cool in the pan for about 10 minutes, then transfer to a cooling rack to cool completely.