Dice the onion into 1/2-inch pieces, mince the garlic, and drain and rinse the white beans. Pat the chicken breast dry and season both sides generously with salt and black pepper. Having everything prepped and ready will ensure smooth cooking without interruption, which is especially important for building a cohesive soup base.

Heat the olive oil in a large pot over medium-high heat until shimmering. Add the seasoned chicken breast and cook for 2 minutes per side until golden brown—this develops crucial flavor through browning. Transfer the chicken to a plate to rest. The fond (browned bits) left in the pot will become part of your flavor base, so don't wipe the pot clean.

Reduce heat to medium and melt the butter in the same pot, scraping up any browned bits. Add the diced onion and minced garlic, cooking for 3 minutes until softened and fragrant. Sprinkle the flour over the vegetables and cook for 2 minutes, stirring constantly—this creates a roux that will thicken your soup. Pour in the chicken broth while stirring to deglaze the pot and incorporate all those flavorful browned bits into your base.

Increase heat to medium-high and add the milk, cumin, coriander, and jalapeños (seeds removed for controlled heat). Whisk continuously for about 5 minutes as the soup simmers and thickens from the roux. I find that freshly ground cumin makes a noticeable difference in depth of flavor, so it's worth seeking out if you can. Watch the consistency—you want it creamy and pourable, not too thick.

While the soup simmers, shred or chop the rested chicken breast from Step 2 into bite-sized pieces. Reduce heat to medium-low and whisk the sour cream into the soup until fully incorporated—this adds richness and prevents lumps. Add the corn, beans from Step 1, and shredded chicken, then simmer for 1 minute until everything is heated through. I like to let the soup rest for 2-3 minutes before serving so all the flavors can meld together.

Taste the soup and adjust seasoning as needed with the remaining salt and black pepper. Remember you already seasoned the chicken and added salt in the broth and initial seasoning, so add salt gradually and taste between additions to avoid over-seasoning. Ladle into bowls and serve hot.