Melt butter in a large skillet over medium heat. Add diced onion and celery, sautéing for 3-4 minutes until softened and fragrant. This soffritto base adds depth to your chowder.

Transfer the sautéed vegetables to your slow cooker. Add diced potatoes, corn kernels, broth, salt, pepper, thyme, and bay leaves. Stir well to combine all ingredients.

Cover the slow cooker and set to low heat. Cook for 6-7 hours, or on high for 3-4 hours, until the potatoes are completely tender.

In a small bowl, whisk together cornstarch and 3 tablespoons of cold water until smooth. Pour this slurry into the slow cooker and stir well to distribute evenly.

Add the heavy cream and milk to the slow cooker, stirring gently to incorporate. The mixture should begin to thicken as it sits.

Cook on high for an additional 15-20 minutes, stirring occasionally, until the chowder reaches your desired thickness and the cream is fully heated through.

Taste and adjust seasonings as needed. Remove bay leaves before serving. Ladle into bowls and serve hot, optionally garnished with fresh parsley or crispy bacon bits.