Add the peeled garlic cloves to ¼ cup of olive oil in the bottom of a dutch oven. Heating the garlic in the oil helps infuse the oil with more flavor.
When the oil is hot, add the finely sliced onions and saute until they soften, then add all of the spices, as well as a pinch of salt. Continue to saute the onions, along with the spices, until the spices are fragrant.
Add the cut up squash to the dutch oven and toss with the onions and spices to coat, then sprinkle over 1 tablespoon of flour. Toss this a few times and cook for a minute.
Add the stock to the rest of the ingredients, stirring constantly. Bring to a boil, then reduce heat to simmer and allow the soup to simmer until the squash is fork-tender, about 15-20 minutes.
Puree the soup with an immersion blender, or by transferring it to a blender, working in batches if needed. Be careful not to overfill the blender with hot soup.
Transfer the soup back to the dutch oven and keep warm until ready to serve. Adjust for salt, if necessary, and top with a spoonful of yogurt and fresh mint to serve.