Step 1Heat the oven to 350 degrees.
Step 2In a large, heavy-bottom saute pan, heat the olive oil over medium-high heat. Stir in the sausage and cook until browned on all sides and cooked through, about 5 minutes.
Step 3Add the wine and cook, scraping the flavoring from the bottom of the pan. Continue to cook until the wine reduces and is mostly evaporated, 1 to 2 minutes. Decrease the heat to medium.
Step 4Stir in the kale, one handful at a time. Cook the kale, stirring it in with the sausage, until it begins to wilt and turn a bright green. Continue adding kale by the handful until it is all added to the saute pan and is just wilted. Do not overcook the kale. Remove from heat and set the pan aside.
Step 5In a large saucepan, melt one-half cup (1 stick) butter over medium heat. Whisk in the flour to form a roux. Slowly add the milk, whisking constantly to get rid of any lumps. Bring the mixture to a simmer, whisking frequently. Reduce the heat to a gentle simmer and cook for 10 minutes.
Step 6Crumble the goat cheese to the sauce and whisk until the cheese is melted and the sauce is smooth, then stir in the sausage and kale. Remove from heat.
Step 7Spoon the mixture into a shallow, 2-quart gratin dish.
Step 8In a medium bowl, combine the Parmigiano-Reggiano, bread crumbs and minced fresh herbs. Pour over the 3 tablespoons melted butter and stir until the butter is evenly distributed to form the topping.
Step 9Sprinkle the topping evenly over the sausage and kale mixture.
Step 10Bake the gratin until the topping is golden-brown and the filling is bubbly, about 30 minutes.
Step 11Cool slightly before serving.