Sauté the aromatics: In a large pot, warm the butter or oil over medium heat. Add onion and a pinch of salt.
Cook 4–5 minutes until soft and translucent. Stir in garlic and jalapeño; cook 1 minute until fragrant.
Toast the spices: Add chili powder, smoked paprika, and cumin. Stir 30 seconds to wake up the flavors without burning.
Add the corn: Stir in the corn kernels.
Cook 3–4 minutes so the corn warms through and picks up the spices. If using fresh corn, let a few bits lightly caramelize for extra flavor.
Pour in broth: Add the broth and bring to a gentle simmer. Reduce heat and cook 10 minutes to blend the flavors.
Blend for creaminess: Use an immersion blender to blend about half the soup right in the pot until slightly thickened, leaving some kernels whole.
If using a countertop blender, carefully blend 2–3 cups and return it to the pot.
Make it silky: Stir in the heavy cream and mayo. Simmer on low 2–3 minutes. Do not boil after adding dairy.
Brighten and season: Stir in lime juice and Cotija.
Taste and season with salt and pepper. Adjust chili powder, lime, or a splash of hot sauce if you like more kick.
Garnish and serve: Ladle into bowls. Top with extra Cotija, cilantro, green onions, a dusting of chili powder or Tajín, and a squeeze of lime.
Serve hot.