Warm potato salad with smoked trout and arugula

Spring is coming on slowly here in Park Slope. We’ve had a few days whose low clouds keep it warm, and every day there are new buds on the trees. It’s welcome, though less exciting is waking up on a morning like this one, grey and rainy.
Good thing all of yesterday was spent walking around the neighborhood, finding gems like the market up 7th avenue that sells spices in bulk, and Alchemy, with its two-for-one happy hour, which meant that most of late afternoon was spent shooting the shit over the dark bar and an IPA, and then another. Shayla and I left around six, laughing uproariously, and after the walk home arrived hungry.
    It was warm enough for a salad-meal, which reminds me of France and of summer, both of which sound good at the moment. It takes no time to prepare, and this type of meal makes good use of anything that happens to be on hand.
    There was a new fishmonger at the farmer’s market. I often stop by the Union Square Greenmarket on my lunch-break, which doesn’t really lend itself to buying fresh fish, but they had some smoked bluefish for about $7 a pound. The best part about the market is people don’t blink when you buy a dollars’ worth. So that went into the salad, along with two stray potatoes, the last of the tender arugula, and part of a bunch of asparagus. Along with some buttered toast and a bottle of wine, it made summer come despite the rain. 

For salad:

2 large or 6-8 small waxy potatoes, such as Yukon gold
2-3 handfuls fresh, good quality arugula, washed well
2-4 ounces smoked trout or other white fish (1-2 fillet)
4-6 asparagus stalks

For dressing:
adapted from Ina Garden

2 tablespoons champagne vinegar (can substitute other light vinegar, lemon juice, or a combination, but not balsamic)
1/2 teaspoon Dijon or rustic Dijon mustard (I like the grain kind for texture)
1/2 teaspoon kosher salt, or to taste
1/4 teaspoon fresh ground black pepper
1/3 cup olive oil
1 egg yolk, at room temperature (optional)

Cut the potatoes into large cubes, and put into a pot of salted water. Bring to a boil, then turn down and simmer soft. In the meanwhile, cut the bottoms off the asparagus, and slice into 1 ½ inch pieces. Add to the potato pot during the last minute or two of cooking.

Flake the fish into pieces, and set aside.

While the potatoes are cooking, put the first four dressing ingredients in a medium-large serving bowl. Whisk together, and then slowly add the olive oil. For a creamier dressing, add the egg yolk in the same manner. Whisk to emulsify.

When the potatoes and asparagus are done, drain, give a quick rinse, then toss in the dressing while still warm. Add the trout, and garnish with arugula. Serve warm, or at room temperature.