Preheat oven to 350 degrees F. Grease an 8×8 baking pan with butter or nonstick spray liberally.
In a large bowl, combine melted butter with sugar and vanilla extract, whisking until combined and almost smooth. Whisk in each egg one at a time, stirring until a smooth batter forms. Stir in oil and melted chocolate. Add in flour, cocoa powder, baking soda and salt, stirring until combined. Fold in chocolate chips. Spread batter in the 8×8 baking dish and bake for 25-30 minutes until set. Remove and let cool.
Pop popcorn and coat with melted butter and sea salt, tossing well. Melt milk chocolate and stir in coconut oil until completely smooth.
Once brownies are cool, remove them from the pan in one bit square. Set them on a sheet of parchment paper and cut into equal pieces, but keep the brownies pushed together into one big square. Slicing them ahead of time just makes it simpler so you don’t have to cut through the popcorn. Add a drizzle of condensed milk on top of the brownies and add a layer of popcorn. Continue to drizzle and layer popcorn on top (you do not have to measure anything purposely – it’s all fun!) until the popcorn is sort of “stuck” to the brownies and each other. It will never be super sticky and in one piece, but that’s the fun of it – this way it’s truly like buttery popcorn and not like caramel corn. Drizzle chocolate over top.
Let brownies sit for about 20-30 minutes so the chocolate can firm up a little, then serve immediately. These really do need to be eaten the day they are made since the popcorn is fresh.