Preheat oven to 350°F (175°C) and line an 8 × 8-inch pan with parchment.
Whisk melted butter, oil, granulated sugar, and brown sugar.
Add eggs one at a time and whisk well.
Mix in vanilla.
Separately whisk cocoa powder, flour, and salt.
Fold the dry ingredients into the wet mixture.
Fold in chocolate chips.
Spread batter into the prepared pan.
Bake for 24–30 minutes, until a tester has moist crumbs but no raw batter.
Cool for 20 minutes in the pan, then transfer to a rack and cool completely.
Refrigerate for 20–30 minutes if you want cleaner cuts.
Cut into 12 rectangular brownies.
Melt white chocolate gradually in short microwave intervals.
If necessary, thin with a tiny amount of neutral oil.
Attach two candy eyes to each brownie with a little melted chocolate.
Drizzle irregular white chocolate lines across each brownie to create mummy bandages.
Leave the eyes partially exposed.
Allow the chocolate to set before serving.