Peel and chop russet potatoes into even chunks. Place them in a pot and cover with cold, salted water. Bring to a boil and simmer for 15-20 minutes until fork-tender. Drain and mash with butter and milk.

Heat a tablespoon of olive oil in a skillet. Season shrimp with Cajun seasoning and cook for 2-3 minutes on each side until pink and opaque. Set aside.

In the same skillet, melt a tablespoon of butter and cook salmon fillets skin-side down for 4-5 minutes. Flip and cook for another 4-5 minutes until flaky. Keep warm.

Sauté minced garlic in the skillet until fragrant. Add heavy cream, chicken broth, Dijon mustard, salt, pepper, and smoked paprika. Simmer for 4-5 minutes until thickened.

Return shrimp and salmon to the skillet, spooning the sauce over seafood. Simmer for 2-3 minutes.

Boil green beans for 3-4 minutes until tender-crisp. Drain and sauté with butter, garlic, and red pepper flakes.

Plate the mashed potatoes, top with seafood and sauce, and arrange green beans on the side.