In a skillet, melt 1 tablespoon of butter. Stir in panko bread crumbs and cook, stirring, for 2 to 3 minutes or until golden. Transfer to a bowl and set aside.

In a large skillet, melt the remaining butter over medium-low heat. Add the shallots and cook until soft and translucent; about 2 to 3 minutes. Add the garlic and cook for another minute. Be careful not to let them brown.

Stir in the flour, salt, pepper, and nutmeg and let cook for 30 seconds. Gradually add the half and half, stirring constantly, and bring to a gentle boil. Let cook, uncovered and stirring occasionally until the sauce thickens and coats the back of a wooden spoon. Stir in the parmesan cheese.

When the sauce is ready, stir in the baby spinach leaves and cook until wilted and combined with the sauce. Taste and adjust seasoning as needed. Serve warm, topped with toasted panko bread crumbs.