Place the pork in a large bowl and add the brown sugar, sage, salt, garlic powder, smoked paprika, black pepper and red pepper flakes. Mix well using your hands. Form patties from heaping 1/4 cups of the mixture, about 1/3-inch thick.
Melt the butter in a large cast-iron skillet over medium-high heat. Cook the sausage patties in two batches until the internal temperature reaches 160 degrees F, about 5 minutes per side.
