In an electric stand mixer fitted with the paddle attachment, add the brown sugar, butter and olive oil and mix on medium for 4 to 5 minutes, or until light in color and texture and well blended. With the mixer on low, add in the eggs, one at a time, completely mixing the first before adding the second. Take care to scrape down the sides and bottom of the bowl so that everything is incorporated. Add the vanilla, baking powder, baking soda, salt and mix for 1 minute more or until combined. Add in the flour and mix on low until just combined.