3 tablespoons unsalted butter
2 tablespoons canola or other neutral tasting oil
4 ounces semisweet chocolate, coarsely chopped
3/4 cup packed dark brown sugar
1/4 cup white sugar
2 teaspoons pure vanilla extract
1/2 teaspoon fine salt
2 large eggs, cold
1/4 cup cocoa powder
3/4 cup all-purpose flour
1/4 teaspoon baking soda