Heat oil in a large pot over medium heat. Cook garlic and leek until soft and translucent, about 4 minutes. Add apple, celery, and ginger, and cook for 3 minutes. Add sweet potatoes and stock, and simmer until sweet potatoes are tender, about 15 minutes. Add chipotle chile.
Working in batches, transfer mixture to a blender, and puree until smooth, transferring soup to a large bowl as you work. (For safety, remove cap from hole in lid, and cover with a dish towel to prevent spattering.) Season with salt and pepper. Sprinkle with pepitas before serving.
Only use one chile! I only used two and it was still hot. The pumpkin seeds at the end really make a big difference. I also added some greek yogurt as a garnish to balance out the flavors. Also, just added a little more water so it was not so much like baby food. Overall good!
This is a very tasty and a lovely fall recipe! One suggestion, and maybe it was me, but I misread the chipotle chile line item. I read, 1 medium can of chipotle chiles in adobo sauce. Yes, I put the whole can in, 9 chiles in fact. Made a delicious "curry" topping though, with beef and a few potatoes and carrots. I made a new batch of the soup without the chiles to cut the fire of my first mistake. Still spicy but my lips and mouth thanked me. Definitely only 1 chipotle chile is needed.