Poke holes all over the sweet potatoes with a fork. Roast the sweet potatoes whole at 425 F for about 40-45 minutes or until tender. This step can be done a day or two before you want to make the muffins.Just store them in the refrigerator.
When you’re ready to make the muffins, peel the sweet potatoes and mash them with a fork. Set aside and discard the skins.
Preheat the oven to 350 F and line a muffin tin with liners.
Mix the milk and vinegar together and set aside for at least 5 minutes or until the milk curdles.
In a large bowl or a bowl of a stand mixer, mix the mashed sweet potatoes, eggs, brown sugar, olive oil, and the milk/vinegar mixture.
In a separate bowl, whisk together the flour, salt, baking soda, baking powder, cinnamon, and nutmeg.
Add the dry ingredients to the wet ingredients and stir until combined.
Add about 2-3 tbsp of the batter into each muffin tin. Bake for 20-25 minutes or until a toothpick inserted comes out clean. Serve warm or at room temperature.