Garnish with diluted plain Greek yogurt ( or sour cream) – see notes, fresh dill and chive blossoms
Place potatoes in a small pot, cover with water and bring to a boil over high heat. Cover, turn heat down and simmer until fork tender, about 15-25 minutes depending on size.
Make the Dill Sauce. Place water, olive oil and spinach in a blender and blend. Add dill, scallion, salt and pepper and blend until smooth. Taste, adjust salt, add more if you like and a squeeze of fresh lemon juice. Place in a small pot, set aside.
Place seeds, salt and pepper on a small plate and mix well. Coat all sides of ahi with the seed/salt mixture, pressing seeds in firmly.
Cook the Ahi. Heat oil over medium high heat in a cast iron skillet until hot and just smoking. Place ahi gently in the skillet and cover partially if seeds begin to spatter.Sear on very hot heat, for just 1-2 minutes, until it develops a nice golden brown crust, then turn over, and cook the other side, just 1 minute or so. You want the inside to stay rare.
Heat the small pot of green dill sauce over low heat, gently warming, careful not to overheat, or it may loose its vibrant color.
Assemble the plates. Place a circle of green dill sauce in the middle of the place. Slice potatoes and place them over the green sauce. Slice the Ahi with a very sharp knife and place atop the potato slices. Garnish the plate with the diluted yogurt or sour cream, sprigs of fresh dilll and chive blossoms.
Notes: to make diluted yogurt- place equal parts plain yogurt ( or sour cream) and water in a small bowl and stir with a fork until smooth. 2-3 tablespoons of each.