Line a 33 x 46 cm / 13 x 18 inch rimmed sheet pan with parchment. Stir the miso, mirin, soy sauce, maple syrup, 1 tsp sesame oil and ginger in a small bowl until smooth. Pat the salmon dry, set it skin-side down on the pan and spread the glaze over the flesh. Refrigerate for 15 minutes and heat the oven to 220 C / 425 F with a rack in the middle during that time.
Rinse the rice in cold water through about 3 changes until it runs mostly clear, then drain. Combine it with the 360 ml water and 1/4 tsp salt in a 3-quart / 2.8 L saucepan. Slice the scallions.
Bring the rice to a boil over high heat, cover, and turn the heat to low. Cook for 15 minutes without lifting the lid, then take it off the heat and leave it covered for 5 minutes.
About 5 minutes after the rice goes on, wipe most of the marinade off each fillet with your fingers so only a thin film remains. Bake on the middle rack for 12 to 14 minutes, until the thickest part reads 145 F / 63 C and the flesh is opaque and flakes with a fork.
When the salmon goes into the oven, bring 1 liter / 4 cups water and 1/2 tsp salt to a boil in a 2-quart / 1.9 L saucepan. Add the edamame and cook for 4 minutes, then drain and toss with the rice vinegar and 1 tsp sesame oil.
Rest the salmon for 2 minutes and fluff the rice with a fork. Divide the rice among 4 plates, about 140 g each, and top with the edamame and a salmon fillet. Scatter the scallions and sesame seeds over the top and serve.