Step 1: Prepare the Meat Filling: In a medium skillet, heat olive oil over medium heat. Add ground meat and cook, breaking it up with a spoon, until browned. Drain any excess fat. Add diced onion and cook until softened, about 3-5 minutes. Stir in minced garlic, Worcestershire sauce, and dried thyme. Season with salt and pepper. Cook for another minute until fragrant. Remove from heat and let cool slightly. If using, stir in shredded cheddar cheese.
Step 2: Prepare the Potato Mixture: In a large bowl, combine cold mashed potatoes, beaten egg, 1/4 cup flour, chopped chives (or green onions), and garlic powder. Season generously with salt and black pepper. Mix until well combined, but do not overmix, as this can make the potatoes gummy.
Step 3: Form the Pancakes: Place the remaining 1/4 cup flour in a shallow dish. Take about 1/4 cup of the potato mixture and flatten it into a disc in your palm. Place a tablespoon of the cooled meat filling in the center. Carefully bring the edges of the potato mixture together to enclose the filling, shaping it into a patty or disc. Gently dredge each stuffed potato pancake in the flour, coating lightly. Repeat with the remaining potato and meat mixture.
Step 4: Fry the Pancakes: Heat 2 tablespoons of vegetable oil or butter in a large non-stick skillet over medium heat. Once hot, carefully place 3-4 stuffed potato pancakes in the skillet, ensuring not to overcrowd. Cook for 4-6 minutes per side, or until golden brown and crispy. Add more oil/butter as needed for subsequent batches.
Step 5: Serve: Remove the Savory Meat Stuffed Mashed Potato Pancakes from the skillet and place them on a plate lined with paper towels to drain any excess oil. Serve immediately with your favorite toppings like sour cream, applesauce, or a fresh green salad.