Place the chilled mashed potatoes in a large mixing bowl. Sprinkle with flour, chopped herbs, salt, and pepper. Mix thoroughly until the ingredients are well combined and the mixture is cohesive but still soft.
Divide the mixture into four equal portions. Gently shape each into a round, flat patty about 1/2 inch thick, pressing lightly to compact the mixture. Place aside on a plate.
Heat a skillet over medium heat and add a tablespoon of butter and a tablespoon of oil. Once melted and shimmering, test the heat by adding a tiny bit of mixture; it should sizzle immediately.
Gently place the patties into the hot skillet, cooking in batches if necessary. Cook for about 3-4 minutes on each side, until the outer surface is golden brown and crispy, and the interior is heated through.
Carefully flip the patties using a spatula, ensuring they keep their shape and become evenly browned. The sizzling sound indicates they are crisping nicely.
Once both sides are crispy and golden, remove the patties from the skillet and place them on a paper towel-lined plate to drain any excess oil.
Serve the herb mashed potato patties hot, ideally garnished with extra herbs or a dollop of sour cream if desired. Enjoy their crispy exterior and tender, flavorful interior.
