Bring water to a boil, add 1 tsp of salt and cook pasta according to package directions.

Preheat the oven to 200C/400F.

Make the cream sauce by melting the butter in a large pan and sautéing chopped onion with fresh tarragon in it over low heat until onion is tender and tarragon is fragrant for approximately 7 minutes.

Add flour and cook while stirring for one minute, then add wine, let it bubble for a few seconds, then add cream, mustard and capers, cook for additional 3-4 minutes over medium heat until the sauce thickens slightly, add salt to taste and take it off the heat.

Drain pasta when cooked and add directly to the sauce, then add drained tuna, chopped kale, gently toss to combine, add additional salt if needed.

Sprinkle with cheese and breadcrumbs (* At this point you can freeze the casserole and cook it at a later date.) Or if cooking immediately, bake in the preheated oven uncovered for 20 minutes until the top is golden and the tuna noodle casserole is heated through.