Yukon Gold and Sweet Potato Gratin

Ingredients

• 6 tablespoons butter divided room temperature ()
• 2 teaspoons thyme leaves fresh
• 1  garlic clove pressed
• 0.1 teaspoon ground nutmeg 
• 1 teaspoon ground pepper black
• 1 tablespoon kosher salt 
• 1.5 pounds red-skinned sweet potatoes peeled (yams)
• 1 cup whipping cream 
• 2 cups milk whole
• 2.3 pounds yukon gold potatoes rinsed

Equipment

• sauce pan
• oven
• aluminum foil
• glass baking pan

Directions

1. Preheat oven to 400°F. Coat 13x9x2-inch glass baking dish with 2 tablespoons butter. Thinly slice all potatoes; place in prepared dish. Bring milk and next 5 ingredients to boil in medium saucepan; pour over potatoes. Dot with 2 tablespoons butter. Cover with foil.
2. Bake until potatoes are tender and milk is almost absorbed, about 50 minutes.
3. Bring cream to boil in saucepan. Uncover potatoes, pour cream over, and dot with 2 tablespoons butter.
4. Bake uncovered until top is golden brown in spots, about 25 minutes. Cool slightly.