Preheat oven to 350˚F.
For Pesto: Place garlic and pine nuts into the well of a food processor and pulse 4 to 5 times. Add basil to garlic and pine nuts mixture and blend together; with the motor running, add oil in a slow and steady stream until fully incorporated. Transfer pesto to a small bowl and fold in grated Parmesan. Season to taste with salt and pepper.
For Buttered Spätzle: In a medium bowl combine flour and salt and whisk together. In a small bowl combine eggs, milk and melted butter and whisk together. Pour egg mixture into flour mixture and whisk together until smooth (batter should be thick).
Fill a large pot with water and place over high heat. Once water comes to a boil, add small handful of salt.
Using a spätzle maker, or colander with wide holes, add 1 cup batter and push batter through holes into the boiling water. Boil spätzle for 3 to 4 minutes or just until spätzle floats.
Using a slotted spoon, drain and transfer spätzle to a large bowl and repeat until all spätzle has been made.
Place a large skillet over medium-high heat and melt remaining 2 tablespoons butter. Add spätzle and cook, stirring gently, for 4 to 5 minute, until lightly browned and slightly crisp. Season with salt and pepper, gently toss together and transfer to a large mixing bowl. Keep warm.
For Bake: Clean out skillet used for spätzle and place over medium-high heat. Add 1 teaspoon of oil, followed by sausage and saute for 3 to 4 minutes or until the edges begin to brown and caramelize. Remove sausage from skillet and transfer to mixing bowl with spätzle. Add remaining oil to skillet and saute kale for 5 to 6 minutes or until wilted but still firm and crisp. Season with salt and pepper. Transfer kale to bowl with spätzle and sausage.
Lower heat of stovetop to medium and melt butter. Add garlic and shallot and saute for 2 to 3 minutes. Add cream and bring to a boil, reduce heat to medium-low and simmer until cream has reduced by 1/3. Season with salt and pepper. Stir in 2 tablespoons Parmesan and simmer until mixture thickens, 1 to 2 minutes. Remove from heat and stir in pesto until fully incorporated.
Pour pesto cream sauce over the sausage mixture and fold together until completely combined and everything is evenly coated.
Pour mixture into a lightly greased 9”x 13” baking dish and top with remaining grated Parmesan. Bake for 20 to 25 minutes or until casserole is bubbling and the top has browned slightly. Remove from oven, cool for 10 minutes and serve.