Make the paste: Combine the oil and garlic in a small, heavy-bottomed saucepan. Place over low heat and cook until the garlic just barely begins to brown around the edges, 1 to 2 minutes. Add the ground coriander and cumin, and cook 1 minute, stirring constantly. Stir in the chili powder and black pepper and cook, stirring, 2 minutes longer. Add the sage and verjus, bring to a simmer, and cook until reduced and thickened to a paste, 1 to 2 more minutes. Remove from the heat, transfer to a bowl, and cool completely before using.
Use your fingers to coat the salmon all over with the cooled chili paste. Cover and refrigerate for 2 hours.
Wipe the paste from the salmon.
Heat the oil over medium heat in a skillet large enough to hold all the salmon fillets. Sprinkle the salmon fillets with salt, place them in the pan, and cook gently until well browned and just cooked through, 3 to 4 minutes per side. Transfer the salmon to warm plates and serve immediately.
Recipe courtesy of Second Helpings from Union Square Cafe (HarperCollins, 2001) by Danny Meyer and Michael Romano