1. I think butter lettuce is the same thing as Boston lettuce (which is what I found at my grocery store).
2. What are "slender pink French breakfast radishes"? I used sliced regular old radishes.
J-G's BUTTER LETTUCE, RADISH, AND AVOCADO SALAD WITH MUSTARD DRESSING
1 tablespoon red wine vinegar
2 1/2 teaspoons Dijon mustard
Kosher salt and freshly ground black pepper
2 tablespoons grapeseed or other neutral oil
2 teaspoons extra-virgin olive oil
1 head butter lettuce, torn
8 slender pink French breakfast radishes or baby round red radishes, halved
1 scallion, white and pale green parts only, thinly sliced at an angle
2 tablespoons roughly chopped fresh dill
1 avocado, halved, pitted, peeled, and sliced
Whisk together the vinegar and mustard with a pinch each of salt and pepper. Continue whisking and add the oils in a slow, steady stream until the mixture is emulsified.
Toss the dressing with the lettuce, radishes, scallion, and dill. Top with the avocado and serve.