Bring a large pot of water to a rolling boil. Cut the leaves off the ramps and rinse. Fill your largest mixing bowl halfway with ice cubes, water and around 2 Tbsp of kosher salt and submerge the bottom of a colander into the ice water. Once the water is boiling, cook the ramps leaves for 60 seconds, drain and place the leaves into the colander in the ice water. (This stops the cooking process abruptly and preserves the leaves' color and bite). Move the leaves around in the ice water until completely cooled and drain. Form the leaves into a ball between your palms, squeeze out any excess water and place the leaves in the fridge.

Stir together the egg yolk, mustard and balsamic in a deep, but not too large, mixing bowl. Pour the olive oil into a measuring cup. Drip the oil into the bowl slowly while simultaneously whisking the mixture with a hand mixer or whisk. Don’t rush it, especially in the beginning, or the emulsion will break and the oil will separate from the other ingredients. (If this happens, start with another egg yolk and add the broken mixture, drip by drip, while whisking as above. Then whisk in the remaining oil.) Stir in 1 tsp of fine sea salt, taste and add more salt, mustard or vinegar as needed. 

Separate the ramps leaves into 6 equal bunches and place in small serving bowls. Give the mustard mayonnaise a fresh stir and spoon half of it over the ramps leaves in the bowls. Serve with chopsticks and let your eaters stir the mayonnaise into the leaves.