In a small skillet, melt butter over medium-low heat until melted. Don't cook butter for too long or the liquids will begin to evaporate. Remove from heat and pour into mixing bowl.
Add oil, brown sugar, and sugar to butter in a mixing bowl. Cream for 4-5 minutes.
Add eggs and vanilla. Cream for 1 minute longer.
Stir in flour, baking soda, and salt. Stir just until combined.
Stir in dark chocolate chunks or chips.
Wrap or cover dough. Chill for at least 30 minutes, several hours, or overnight.
Preheat oven to 385 degrees.
Bake for 9-11 minutes or until edges begins to turn a light golden brown. Watch carefully. Once there is about 1 minute left, open the oven, and sprinkle the cookies with sea salt flakes.
Remove from oven and let set up for several minutes before removing to cooling rack.