Step 1

In a saucepan, heat the olive oil until shimmering. Add the onion, garlic and a generous pinch of salt and cook over moderate heat, stirring, until softened and starting to brown, 8 minutes. Stir in the tomatoes, chipotle chiles and stock and bring to a boil. Simmer over moderately low heat, stirring occasionally, until the tomatoes are very soft, 30 minutes.

Step 2

Meanwhile, in a skillet, heat 1/4 inch of canola oil. Add half of the tortilla strips and fry over moderate heat, stirring, until crisp, 2 to 3 minutes. Using a slotted spoon, transfer the strips to paper towels. Season with salt. Repeat with the remaining strips.

Step 3

Carefully ladle half of the soup into a blender and add half of the butter. Puree until smooth. Pour the pureed soup into a large saucepan. Repeat with the remaining soup and butter. Stir in the shredded chicken and gently reheat the soup. Season with salt.

Step 4

Serve the soup in bowls, garnishing with queso fresco, chile, cilantro and tortilla strips.