Broccoli Cheddar Potato Pierogi

Name: Broccoli Cheddar Potato Pierogi
Prep time: 1 h
Cook time: 30 min
Total time: 1 h 30 min
Cuisine: European
Ingredients: 2 cups all-purpose flour; 1 teaspoon kosher salt; 2 tablespoons salted butter, melted; 1 cup plain full-fat greek yogurt; 1 large egg; 3 Russet potatoes, peeled and quartered ((about 1 pound)); 2 cups broccoli florets; 2 tablespoons salted butter, at room temperature; 2 cups shredded sharp cheddar cheese; 2 ounces cream cheese, at room temperature; 1 teaspoon dried thyme; 1/2 teaspoon garlic powder; 1/2 teaspoon onion powder; 1/4 teaspoon cayenne pepper; kosher salt and black pepper; 4 tablespoons salted butter; 1 yellow onion, chopped; 1 tablespoon fresh thyme leaves