Bring a medium pot of lightly salted water to a boil. Thoroughly rinse produce and pat dry. Peel and finely mince shallot. Stem and roughly chop tarragon sprigs. Rinse salmon fillets and pat dry.

Place salmon, 1 tsp. salt, and apple cider into a shallow dish or bowl. Allow salmon to marinate in the apple cider brine for 15 minutes, flipping halfway through. Remove salmon from the brine and pat dry with a clean dishcloth or paper towel.

Add green beans to the pot of boiling water, reduce heat to low, and cook until beans become fork tender, about 4-5 minutes. Drain water and set green beans aside on a plate. Using the same pot, heat 2 tsp. olive oil and shallots over medium heat and sauté for 1-2 minutes. Add the green beans and cook for another 2-3 minutes. Season with a pinch of salt and pepper. Set aside.

Season both sides of salmon with a pinch of salt and pepper. Heat 2 tsp. olive oil in a medium pan over medium heat. Once oil is warm, add salmon and cook on each side for 4-5 minutes, or until a minimum internal temperature of 145 degrees is reached. Wipe out pan.

In the pan you used to cook the salmon, add mustard, heavy cream, and tarragon (reserving a pinch for garnish). Stir ingredients together over very low heat until combined and slightly thickened, about 3-5 minutes, taking care not to burn the sauce. Season with a pinch of salt and pepper.

Place a piece of salmon in the middle of the plate. Compose a mound of green beans and shallots next to the salmon. Spoon the tarragon and mustard cream sauce over the salmon. Garnish with any remaining tarragon and a crack of fresh black pepper.