Place peeled and quartered potatoes in a large pot. Cover with cold water by about an inch. Add 1 tsp salt. Bring to a boil over high heat, then reduce heat to medium-low and simmer until fork-tender, about 15-20 minutes.

While potatoes cook, gently warm the milk and 1/4 cup butter in a small saucepan or microwave-safe bowl. Stir in the minced garlic and chopped chives. Keep this mixture warm.

Drain the cooked potatoes thoroughly. Return them to the hot pot over low heat for 1-2 minutes, stirring occasionally, to evaporate any excess moisture. This ensures fluffy mashed potatoes.

Mash the potatoes using a potato masher or ricer until smooth. Gradually add the warm milk-butter mixture to the mashed potatoes, whisking vigorously until creamy and smooth. Season with additional salt and pepper to taste. Cover and keep warm.

Pat the ribeye steaks very dry with paper towels. Season generously all over with coarse sea salt and freshly ground black pepper. Allowing them to sit at room temperature for at least 20-30 minutes helps achieve a better sear.

Heat a large cast-iron skillet (or a heavy-bottomed pan) over high heat until it just begins to smoke (about 3-5 minutes). Add the olive oil and swirl to coat the pan.

Carefully place the seasoned steaks in the hot skillet. Sear undisturbed for 2-3 minutes per side until a deep brown crust forms. If cooking two steaks, avoid overcrowding the pan; cook them one at a time if necessary to maintain high heat.

Reduce the heat to medium. Add the remaining 1 tbsp butter, smashed garlic cloves, fresh rosemary, and fresh thyme to the pan. Tilt the pan slightly and, using a large spoon, continuously baste the melted butter and aromatics over the steaks for 3-5 minutes, flipping them once halfway through. Continue until desired doneness is reached (e.g., 125-130°F for medium-rare, 130-135°F for medium, checked with a meat thermometer).

Remove the steaks from the pan and transfer them to a cutting board. Tent loosely with aluminum foil and let them rest for 5-10 minutes. This crucial step allows the juices to redistribute, ensuring a tender and flavorful steak.

Slice the rested steaks against the grain, if desired. Serve immediately with a generous portion of the warm garlic herb mashed potatoes. Drizzle any accumulated pan juices from the cutting board or pan over the steak and potatoes. Garnish with extra fresh chives or herbs if desired.