Melt butter and mix in cocoa powder until a smooth paste forms.
Add the cocoa paste, oil, honey, vanilla, and salt to the pan and mix until smooth and well combined.
Add rolled oats and chopped nuts and stir until evenly coated.
Spread evenly and press down firmly to about half an inch depth.
Bake at 325°F (160°C) for 20–25 minutes until the color deepens and you get a roasted aroma.
Cool completely in the pan, then break into clusters or crumbles.
Transfer to an airtight container.