Place the oven rack in the second lower level, preheat the oven to 170 degrees Celsius - 338 Fahrenheit.
Line the muffin sockets with paper cuffs (no more than 3 cm high)
Sift flour into a bowl, add the rest of the dry ingredients and mix well.
Melt chocolate cubes and olive oil in the microwave, transfer to a separate bowl, and mix well; add sugar, milk, vinegar, vanilla, and rum, and mix well.
Transfer the batter to the pan and fill the sockets all the way. You can use a large cookie scoop (see photo at the beginning of the post).
Decorate each muffin with chocolate chips.
Bake for 30-35 minutes until a toothpick inserted in the center of the muffins comes out clean.
Take out and cool on a wire rack. Allow the muffins to cool completely before removing them from the pan.
