Marry Me Scalloped Potatoes

Name: Marry Me Scalloped Potatoes
Ingredients: 3/4 cup drained and chopped sun-dried tomatoes in oil; 1 tablespoon oil from sun-dried tomatoes jar; 1 medium shallot , chopped; 3 cloves garlic , chopped; 1/4 teaspoon salt; 2 teaspoons no-salt-added tomato paste; 1 teaspoon chopped fresh thyme , plus more for garnish; 1 tablespoon all-purpose flour; 2 1/2 cups whole milk; 2 pounds Yukon Gold potatoes , scrubbed and sliced crosswise into 1/8-inch rounds; 3/4 cup grated Parmesan cheese , divided