Craftsteak Spinach Gratin

INGREDIENTS

• 3 Tbs. unsalted butter, plus more for greasing
• 1 cup fresh bread crumbs
• 1/3 cup grated Parmigiano-Reggiano cheese
• 2 tsp. vegetable oil
• 2 lb. baby spinach
• 2/3 cup heavy cream
• 2/3 cup half-and-half
• 1/4 cup diced yellow onion
• 1 Tbs. plus 1 tsp. all-purpose flour
• 1 clove
• Pinch of freshly grated nutmeg
• 1 bay leaf
• 1 fresh thyme sprig, plus leaves from 1 thyme sprig
• 1/2 cup grated Emmentaler cheese
• Kosher salt and freshly ground white pepper, to taste