Heat a 12-inch non-stick saute pan over a high flame. Season the salmon fillets with salt and pepper. Add a small amount of oil to the pan and sear both sides of the salmon quickly, just a few seconds on each side, leaving the fish very rare. Remove the pan from the heat, and place the fish on a work surface. Wipe out the pan and reserve for later use.
Spread a 1/4-inch layer of pesto evenly over 1 side of the fillet. Sprinkle the top of the pesto with a light, thin dusting of fresh bread crumbs. Carefully invert each fillet into the pan and place it over a medium flame. Toast the bread coating, adding tiny bits of butter to the pan that will melt into the salmon underneath. Once the bread is toasted (after about 1 minute), place the pan in the oven for about 3 minutes, just to heat the fish through.
To serve, mound 1/6 of the spinach in the center of a warm dinner plate. Invert 1 salmon fillet onto the spinach, crust-side up, and ladle citrus soy sauce around the sides. Place 1 orange segment on top of 1 grapefruit segment in the sauce at 3 different points on the plate.
In the bowl of a food processor place, pine nuts, garlic, salt, and pepper. Add the basil and process again. With the motor running, add the oil in a stream slowly, scraping down the sides of the bowl occasionally. Add bread crumbs a little at a time, just enough to make pesto spreadable. Process and repeat until the pesto is the right consistency. Remove from food processor and set aside until ready to use.
Citrus Soy Sauce:
Yield:1 1/2 cups
In a non-reactive saucepan, saute the ginger in 1 tablespoon olive oil for 1 minute over medium heat. Add the shallot and garlic and continue cooking for 1 minute longer. Deglaze the pan with white wine, champagne vinegar, soy sauce, fish sauce, and all 3 fruit juices. Reduce the liquid volume down to 1 cup. Add the chicken stock, bring it to a boil, and cook another 3 minutes. Strain, pushing on the solids to extract as much liquid as possible, and place the liquid into a blender or food processor. With the motor running on low, add the remaining olive oil in a slow stream until all the oil is incorporated.
Steamed Spinach Leaves:
Wash spinach thoroughly and drain, leaving some of the water clinging to the leaves. In a 12-inch saute pan over medium heat, saute the spinach in a small amount of olive oil until it is wilted, 1 to 2 minutes. Drain excess moisture, season with salt and pepper.
Preheat oven at 350 degrees.
Peel potatoes and slice thin in a criss-cross cut on the zig-zag part of the mandolin. Lay out the slices on a baking sheet. Brush with clarified butter and bake until crisp, about 12 minutes.