Preheat oven to 350°F. Grease 2 (14oz) or 4 (8oz) ramekins with butter and set aside.
Brown the butter for cookie dough in a pan and pour into a bowl to cool.
For brownie batter: Add ¼ cup butter to a pan over medium-high heat, melt and brown for about 5 minutes. Add cocoa powder while still on heat and stir quickly. Remove from heat and mix in chocolate chips and olive oil until smooth. Set aside.
In a medium bowl, whisk together egg and both sugars until frothy. Mix in vanilla.
Once chocolate mixture is slightly cooled, stream into egg/sugar mixture and whisk.
Fold in flour and salt. Fold in chocolate chips. Set aside.
For cookie dough: In a bowl, whisk together flour, baking soda, baking powder and salt.
Add both sugars to cooled brown butter and whisk. Whisk in egg.
Whisk in heavy cream and vanilla.
Add dry ingredients to wet and fold. Fold in chocolate chips.
Divide half the brownie batter evenly among ramekins and spread. Dollop half the cookie dough and press down. Repeat process one more time.
Bake at 350°F for 20-25 minutes (8oz ramekins) or 25-30 minutes (14oz ramekins) until golden, with edges set and middle still soft.
Remove and cool slightly. Invert warm brookies into a bowl or serve straight from ramekins with flaky sea salt and vanilla ice cream.
