Preheat oven to 350°
Prepare two 9" x 13" sheet pans by lining with parchment paper or silcone baking mats.
Whisk together flour, salt and baking powder in a medium bowl.
Place chocolate chips and butter in a heat-proof bowl. Microwave at 50% power for 30 seconds then stir. Continue to heat at 50% power in 30 second bursts, stirring between each heating, until all chocolate and butter is melted. Take care not to overheat the chocolate as it can scorch easily.
Place the sour cream, oil, egg, granulated sugar and vanilla extract in a large mixing bowl. Combine well using a whisk.
Add melted chocolate and butter to the mixing bowl. Combine well using a whisk.
Add the dry ingredients (flour, salt and baking powder) to the mixing bowl and whisk until well combined.
Set the dough aside for 10 minutes – the mixture will set up slightly.
Scoop the dough onto the parchment-lined baking sheets using a small cookie scooper (approximately 1 ½ tablespoon per cookie). Leave approximately 2 inches of space between each cookie.
Bake cookies for 7 - 8 minutes. Top of cookies will have a slightly crackled surface.
Let cookies cool on the baking sheets for 5 to 10 minutes, then transfer to a wire rack to cool completely.