A melt-in-your-mouth bite-sized appetizer that's big on flavor.
Place your oven rack at the highest notch, then preheat your oven to broil. You can either use a toaster/small convection oven (which I prefer) or your primary oven.
Mix the mayonnaise, egg yolk, sriracha and masago in a bowl with a spoon and set aside. (Feel free to add more sriracha if you like it hot!)
Place a small saucepan on medium heat and combine the soy sauce, dashi granules, mirin and sugar. (I know that a pinch is a very inaccurate amount, but it’s such a tiny amount that I can’t quantify it. Be careful–too much will make the sauce unbelievably salty!)
Stir the sauce until the sugar has melted, then continue to stir slowly until the sauce starts to bubble. Once the color of the sauce becomes a lighter, burnt caramel color, stir quickly and reduce the heat as the bubbles start to rise. Continue to stir and reduce the heat until you reach the lowest setting–by this point, the sauce will be thick and the bubbles will be much smaller. The sauce is done when you can scrape your spoon across the pan and see the bottom of the pan clearly. (You’re looking for a thick, caramel-like consistency.) Set aside; the sauce will harden like caramel, but will liquefy easily with heat when we need it at the end!
Place your salmon filet with the shorter end facing you. With your knife, slice thinly at an angle along the grain of the filet to create a thin salmon strip the length of the filet. Continue until you have about 25-30 strips. Set aside.
Slice an avocado in half and remove the pit. Carefully peel the skin of the avocado. Slice into 1-inch pieces–one avocado should provide anywhere from 25-30 1-inch pieces.
Line a baking sheet with aluminum foil.
Take one avocado piece and lay it on the end of a salmon strip, with the flat end of the avocado facing you. Hold the salmon and avocado together with one hand and roll the other end of the strip around the avocado with the other. This will look similar to a sushi roll–but with salmon on the outside and avocado on the inside! See the photo above for reference. Place the completed salmon-avocado “roll” onto the baking sheet.
Repeat the process until all of the salmon-avocado “rolls” are on the baking sheet with no space in between each roll.
Take your mayonnaise sauce and generously top each roll, allowing the sauce to completely cover the tops. This will give the rolls a mushroom-like appearance.
Place the baking sheet in the oven and watch through the window. The broiling should take no longer than 5 minutes or less. It is very important that you stick around and watch the mushrooms–they can go from bubbling and golden to burnt in less than a minute!
When the top starts to darken and black spots appear, the mushrooms are finished. Take the baking sheet out of the oven.
Re-heat the sweet soy sauce on low heat–it should take less than a minute for the sauce to liquefy. As soon as you are able to stir the sauce without resistance, remove from heat.
Plate the mushrooms, then drizzle sweet soy on top.
Garnish with sesame seeds and scallions and serve immediately.