Blend the berries until smooth, then strain to remove the seeds. Stir in the vinaigrette, reserving ⅓ cup for later.

Place the steak in a food storage bag and pour the remaining berry-vinaigrette mixture over it. Seal the bag and refrigerate for 2 hours, turning the bag occasionally. After marinating, drain the steak.

Preheat your grill to medium-high heat. Grill the steak for 4-5 minutes on each side for medium-rare, flipping once. Let the steak rest for 5 minutes, then slice thinly.

Arrange the next five ingredients on a serving platter. Lay the sliced steak on top, followed by a sprinkle of pepper and nuts. Drizzle with the reserved dressing. Garnish with mint if desired.