Put sausage in a saucepan and cover with water. Place pan on medium-high heat and bring to a simmer for about 10-12 minutes. (Optionally, you can skip this step and just slice the sausage and cook it in butter)

Heat a skillet with butter and transfer the sausages to the pan along with the sliced apple and blackberries. Cook for a few minutes, stirring occasionally until the sausage is browned and the apples have softened. Serve.