Cook coriander seeds in a small dry saute pan just until the aroma is released. Crush seeds using the bottom of a heavy pot or a mortar and pestle. Mix seeds with salt, pepper, and sugar in a small bowl and reserve.
Slice salmon in half across width and lay pieces side by side on counter, flesh-side up. Divide dry spice mixture in half and sprinkle one half over both pieces. Place half the dill sprigs on 1 piece of salmon and top with remaining piece of salmon to enclose the spices and herbs, as if making a sandwich. (Make the sandwich even by placing the thick end of salmon of top of thin end.)
Evenly coat outside of salmon sandwich with remaining spices and dill. Tightly wrap in 2 layers of plastic wrap, place in a shallow baking dish, and top with weights (canned goods or milk cartons are good). Refrigerate 3 days, turning over every 12 hours.
To serve, scrape off spices and dill. Slice thinly and serve cold with Dill Mayonnaise and thinly sliced black bread.
In a bowl, combine egg yolks, mustard, vinegar, and sugar. Blend with whisk. Gradually add olive oil and soybean oil, a drop at a time, whisking constantly. As mayonnaise begins to thicken, add oils more generously. Whisk in dill, salt, and pepper. Adjust seasonings and store in refrigerator up to 4 days.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.
c.1998, M.S. Milliken & S. Feniger, all rights reserved