In medium saucepan, place spelt and a couple of pinches of salt and add enough water to cover grains by 2 inches. Bring to a boil, reduce heat to medium-low, and simmer, covered, until kernels are tender, about 40 minutes. Drain any excess water.

In another saucepan, add water to a depth of about 3 inches; bring to a boil. Using slotted spoon, gently lower eggs into water; boil for exactly 6 1/2 minutes, adjusting heat to maintain a gentle boil. To bowl of ice water, transfer eggs and chill until slightly warm, about 2 minutes. Softly tap eggs against countertop to break shell in several spots and gently peel, starting from wider end containing the air pocket. Cut eggs in half lengthwise.

In skillet over medium, heat grapeseed or sunflower oil. Add dulse and heat, stirring often, until crispy, about 1 minute. Remove from skillet to cool and then chop into 1 inch pieces.

Heat oven to 350 F. Spread walnut halves on baking sheet and heat until they smell toasty and are a couple of shades darker, about 10 minutes, stirring nuts once. In blender container, place walnuts, olive oil, cider vinegar, 1 Tbsp water, horseradish, mustard, garlic, rosemary, salt, and pepper; blend until smooth. If needed, add more water, 1 Tbsp at a time, to help with blending and reach a thinner consistency.

Divide spelt, mackerel, carrot, beets, apple, dulse, and eggs among 4 serving bowls. Drizzle on walnut sauce and top with parsley.