Preheat the oven to 450 degrees F (232 degrees C).
Cut the bell peppers in half and remove the stem and seeds. Quarter the onion, removing the stem and outer peel. Remove the outer paper from the garlic cloves and trim the hard stem off. Place the bell peppers cut side down on a rimmed baking sheet. Add the onions and the whole jalapeno. Drizzle with 1 tbsp olive oil.
To the same baking sheet, add the frozen corn and whole garlic cloves. Toss with the remaining olive oil and all the seasonings. Bake in the preheated oven on the middle rack for 20 minutes, until the skin of the peppers are blistered and the corn is golden on top.
To a metal or glass bowl, add the roasted bell peppers and jalapeño and cover in plastic wrap. Let sit for 10 minutes. Remove the plastic wrap and remove the blistered skin from the peppers. Discard any stems or seeds that remain. For a less spicy soup, discard the seeds from your jalapeño. For more spice, include the seeds.
Working in batches, add the roasted veggies, evaporated milk, and chicken broth to a blender. Blend on high for 30 seconds or until smooth.
Add all the blended soup to a large pot and bring to a simmer over medium heat. Stir in the shredded chicken and canned corn. Simmer for 10 minutes. Add any additional salt, if needed. Serve immediately.