Step 1

Heat olive oil in a 2-quart Dutch oven or large pot over medium heat; cook and stir onion, smoked sausage, and kielbasa sausage in the hot oil until sausage is browned, about 10 minutes. Stir potatoes into sausage mixture and pour in enough water to cover mixture; add bay leaves.

Step 2

Simmer sausage-potato mixture over low heat until potatoes are tender and flavors of soup have blended, 1 to 2 hours.

Step 3

Combine flour and butter in a saucepan over medium heat; cook and stir until mixture is smooth and lightly golden, about 5 minutes. Whisk milk into flour-butter mixture until thickened; season with salt. Stir flour-butter mixture into soup until well combined. Remove and discard bay leaves before serving.