Sweet Potato Tian

Name: Sweet Potato Tian
Ingredients: 6 Tbsp. unsalted butter, plus more for pan; 3 garlic cloves, finely grated; 1 1 piece ginger, peeled, finely grated; 1 Tbsp. finely grated orange zest; ¼ cup fresh orange juice (about 1 orange); ¼ cup low-sodium vegetable broth; ¼ cup light brown sugar; 2 Tbsp. dark soy sauce; 1 Tbsp. white miso; 2 tsp. Diamond Crystal or 1¼ tsp. Morton kosher salt; 2 tsp. five-spice powder; ½ tsp. freshly ground black pepper; 1 Tbsp. thyme leaves, plus more for serving; 4 lb. medium sweet potatoes, unpeeled, sliced ⅛ thick