Chop all of the vegetables: Cut the potatoes into small chunks, mince the garlic, chop the onion, and dice the shallot. Remove the root end from the leek and chop the rest of the leek into small pieces.
In a saucepan on medium heat, add the oil.
Add to the pan the garlic, shallot, onion, and chopped leeks, cooking until tender and caramelized, about 3 to 5 minutes.
Add in the chunks of potatoes to slightly brown them, about 2 minutes.
Add a bit of water into the pan, and then transfer all of the vegetables into a Dutch oven or soup pot.
Dissolve the bouillon cube in 1 cup of water and add it to the pot.
Place the pot on the stovetop on medium heat. Fill it with enough water to reach the top of the vegetables.
Allow the soup to simmer for at least 30 minutes, until the potatoes are tender.
Pour the entire can of coconut milk into the soup. Stir well to combine while using a large spoon to break down the potatoes into a creamy soup.
Reduce the heat to medium-low and allow the soup to set for 10 minutes before serving.
Ladle the soup into bowls and serve it topped with sour cream, cheddar cheese, and chopped scallions.