In a small saucepan over low heat, combine the roasted bone marrow and blackberries. Cook for about 5 minutes, mashing the blackberries with a fork until they release their juices.

Once combined, remove from heat and strain the mixture through a fine mesh sieve, pressing to extract as much liquid as possible. Discard the solids.

In a bowl, mix the strained blackberry juice with softened butter and chopped parsley. Season with a pinch of salt and pepper. Set aside to firm up in the refrigerator.

Preheat your grill or skillet over medium-high heat. Pat the ribeye steaks dry with paper towels and drizzle olive oil on both sides.

In a small bowl, combine the toasted celery seeds and smoked sea salt. Rub this mixture generously over both sides of the steaks.

Place the seasoned steaks on the grill or skillet and cook for 4-5 minutes on each side for medium-rare, or until your desired doneness is reached. Use a meat thermometer for accuracy (130°F for medium-rare).

Once cooked, remove the steaks from the heat and let them rest for about 5 minutes.

Slice the rested ribeyes and plate them. Top each steak with a generous dollop of the blackberry-infused bone marrow butter. Garnish with additional fresh parsley, if desired. Serve immediately and enjoy!