Heat the olive oil in a Dutch oven over medium heat. Add the onion and Fresno and cook, stirring often, until the onions are translucent and tender, 5 to 6 minutes. Stir in the garlic, chili powder, cumin and bay leaf and cook until the spices are fragrant, 1 to 2 minutes. Add the pumpkin puree, then stir and cook until it starts to bubble and brown a bit, 2 to 3 minutes. Add the shredded chicken and season with salt and pepper. Pour in the chicken broth and use a wooden spoon to scrape up any browned bits on the bottom of the pan. Bring to a low boil, then reduce the heat to a simmer and let simmer, stirring occasionally, 1 hour. Stir in the beans and corn and continue to simmer, uncovered, until the liquid has reduced and the chili is thick, about 30 minutes. Cut pumpkins out of the cheese slices with a pumpkin-shaped cookie cutter. Using a paring knife, give each pumpkin eyes, a nose and a mouth to resemble a jack-o'-lantern. Ladle the chili into bowls and top with the cheese pumpkins. Serve with the Greek yogurt, scallions and tortilla chips.