Step 1

Heat butter in a large Dutch oven or other heavy pot over medium-low. Add bacon and cook, stirring often, until brown and crisp, 8–10 minutes. Increase heat to medium and add onion, leek, celery, and bay leaves; cook, stirring often, until onion is translucent and softened, 8–10 minutes.

Step 2

Add potatoes and clam juice to pot; season lightly with salt and generously with pepper. Bring to a simmer and cook, uncovered, stirring occasionally, until potatoes are tender, 10–15 minutes. For a thicker texture, smash several pieces of potato against the sides of the pot. Add trout and buttermilk and simmer about 5 minutes (to give flavors time to blend together). Taste and season with more salt and pepper as desired. Remove from heat and stir in cream.

Step 3

Ladle chowder into bowls, top with trout roe, if desired, and season with coarsely ground pepper.

Step 4

Do Ahead: Chowder can be made 2 days ahead. Let cool; cover and chill. Reheat gently over low before serving.