Preheat oven to 350°F.

In a large mixing bowl, mix together the butter, oil, and sugar until smooth and combined.

Add eggs one at a time, mixing well after each addition. Then add the red food dye, vanilla extract, and vinegar, mixing until well combined.

In a medium bowl, sift together the flour, baking soda, kosher salt, and cocoa powder. Gradually add to the wet mixture in three batches, alternating with the buttermilk, starting and ending with the flour. Mix well after each addition, ensuring there are no lumps.

Spray the mini bundt pan with non-stick cooking spray and fill each cavity 3/4 full with batter. Top with 4-5 chocolate chips.

Bake for 15-18 minutes or until a toothpick inserted comes out clean. Let cool in the pan for 5 minutes before transferring to a wire rack to cool completely.