Melt butter in a large Dutch oven or soup pot over medium heat. Add diced onion and celery, stirring occasionally until softened, about 4-5 minutes. The aromatics should smell fragrant and look translucent before you proceed to garlic.

Stir in minced garlic and cook for 1 minute until fragrant. Add the chicken broth, cubed potatoes, diced carrots, dried thyme, and bay leaf. Bring the mixture to a boil, then reduce heat and simmer for 12-15 minutes until potatoes are completely tender and fork-piercing them meets no resistance.

Pour in heavy cream and whole milk, stirring gently to combine. Season with salt and black pepper, tasting as you go because personal preference matters here. Add the diced smoked turkey and stir until the meat is distributed throughout.

In a small bowl, whisk cornstarch with water until completely smooth with no lumps. Pour this slurry into your potato chowder recipe slowly while stirring constantly for 2-3 minutes. The soup will thicken noticeably as the cornstarch activates in the simmering broth.

Remove from heat and stir in shredded sharp cheddar cheese until fully melted. Taste again and adjust seasonings if needed. Remove the bay leaf before serving—it's purely for flavor infusion.