In a food processor, combine miso, mirin, sugar, chili, ginger, and sake. Puree until you get a fine blend. Add 1/4 cup of water while blending to loosen marinade. Take the marinade and separate 1/4 cup and sit to the side.
Cut the salmon to desired sizes and then coat salmon pieces with marinade. Let the salmon sit in the marinade out on the countertop for 2 to 3 hours.
15 minutes prior to cooking, slice cucumbers and romaine lettuce. On serving plates, create a salad and then place in refrigerator to keep cold.
Preheat the oven to 375 degrees F.
Heat a skillet with olive oil and wait for a light smoke to appear off the surface of the pan. Gently place the salmon filets in the pan and go for a light sear (1-2 minutes).
Flip fish over to the other side, pour the reserved marinade over the top and place in the oven for about 8-10 minutes. Fish should be fully cooked, flaky and tender.
Plate salmon on top of chilled cucumbers and romaine lettuce. Serve immediately.