Potato and Celeriac Root Dauphinoise

Name: Potato and Celeriac Root Dauphinoise
Ingredients: * 1 1/2 cup heavy cream; * 1 cup whole milk; * 2 bay leaf; * 2 garlic clove, smashed; * 1 large thyme sprig; * 1 1/2 pound russet potato, peeled; * 3/4 pound celeriac root, peeled; * 2 tablespoon soft butter; * 1/2 cup panko; * 1/2 cup parmesan; * 2 tablespoon olive oil; * drizzle olive oil; * salt; * pepper