Objection!!! Ketchup + Mayonnaise ≠ Béchamel sauce
sunshinelemons has it correct as aurora sauce
Aurora Sauce
3 Tbsp Mayonnaise
1 1/2 — 3 Tbsp Ketchup
Onigiri
1 1/2 cup sushi rice
1 1/3 cup water
Kosher salt
Water
Wash rice 3 times with cold water then drain.
Add rice to pot and add the measure of water.
Cover the lid and bring it to a boil over medium heat.
Once water is boiling, turn the heat to the lowest setting and continue to cook covered until the water is completely absorbed. ( At 12-13 minute mark, take a quick peek and if there is any water left, close the lid and continue cooking for another minute or so)
Remove from heat and let sit for 10 minutes then fluff the rice and transfer to a plate.
Wet and salt your hands and using your hands form about 1/3 cup of cooked rice into a triangle
Coat onigiri with aurora sauce
Fry in skillet on medium heat until lightly browned
Optional wrap with nori
And serve