Heat butter in large Dutch oven over medium-high heat. When foaming subsides, add onion, celery and ½ teaspoon salt; cook, stirring frequently, until softened, about 3 to 4 minutes. Add garlic and cook until fragrant, about 30 seconds. Add water, ham steak, bacon, peas, thyme, and bay leaves. Increase heat to high and bring to simmer, stirring frequently to keep peas from sticking to bottom. Reduce heat to low, cover, and simmer until peas are tender but not falling apart, about 45 minutes.