Begin by boiling the cubed potatoes in a large pot of salted water until tender, about 15-20 minutes. Drain and return to the pot.
Add milk, sour cream, and 4 tablespoons of butter to the drained potatoes. Mash until smooth and creamy. Season with salt and pepper to taste. Keep warm.
In a large skillet, melt 2 tablespoons of butter over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant.
Add the shrimp to the skillet, sprinkle with paprika, salt, and pepper. Cook for 2-3 minutes on each side until the shrimp are pink and opaque.
Pour in the heavy cream and stir to combine. Let it simmer for another 2-3 minutes until the sauce thickens slightly.
Serve the creamy garlic shrimp over a generous scoop of mashed potatoes. Garnish with fresh parsley.