Peel and cube the sweet potato, then steam or boil until very tender. Drain and mash until smooth.
In a mixing bowl, combine the mashed sweet potato with chickpea flour, whole egg, and egg whites. Season lightly with salt and pepper. Mix until a soft dough forms.
On a lightly floured surface, roll portions of the dough into long ropes about 1/2-inch thick. Cut the ropes into 1-inch pieces to form gnocchi.
Bring a pot of salted water to a boil. Gently drop in the gnocchi and cook until they float to the top, about 2-3 minutes. Remove with a slotted spoon and set aside.
While the gnocchi cooks, slice the turkey sausage into small rounds. In a large non-stick skillet, lightly sauté the sausage slices until browned and heated through. Remove them from the pan and set aside.
In the same skillet, add 1/2 tablespoon of butter and allow it to melt over medium heat. Add fresh sage leaves and let the butter bubble and turn a light brown, releasing a nutty aroma. Be careful not to burn the butter.
Add the cooked gnocchi (and turkey sausage if desired) to the sage brown butter, tossing gently to coat and crisp up slightly on the edges.
Plate the crispy sweet potato gnocchi with the sautéed turkey sausage and drizzle any remaining brown butter over the top. Serve warm and enjoy the harmonious blend of flavors.