Nebraska Handheld Meat Pies

Name: Nebraska Handheld Meat Pies
Ingredients: 1/2 cup warm water (110 to 115 degrees F); 1 packet active dry yeast; 1/4 cup sugar; 3/4 cup milk; 6 tablespoons unsalted butter; 4 1/4 cups all-purpose flour; 1 1/2 teaspoons kosher salt; 3 tablespoons vegetable oil; 1 pound ground beef; 2 1/2 teaspoons kosher salt, plus more if needed; 3 cups chopped green cabbage (about 1/2 large head); 2 cups chopped onion (about 1 large onion); 1 teaspoon ground white pepper; 2 tablespoons unsalted butter, melted, for brushing; Ketchup, for serving