For the candied walnuts, line a baking tray with parchment paper–you’ll need this for the walnuts to cool. Melt the butter and sugar together in a small skillet over low heat. Add the walnuts and salt. Stir constantly until the mixture starts to bubble and thicken, about 1 minute. Continue to stir until the sugar is completely dissolved. (Quick tip–Resist the urge to sneak a bite; the sugar is very hot and you could burn your tongue.) Spread the walnuts out on the lined tray. The glaze will set as the walnuts cool.
To prepare the dressing, add the mustard, both vinegars, olive oil, salt and pepper to an empty jam jar. Screw the lid on tightly and shake vigorously to blend. You will most likely have more dressing than you need for this salad. Store the leftover in the fridge for future salads during the week.
For the salad, gently tear the leaves into bite-sized pieces and place in a large bowl. (Tearing the leaves with your hands instead of using a knife prevents bruising, especially with tender Bibb lettuce, baby mesclun, and other soft greens.) Add the chicken and sliced strawberries to the bowl. The salad may be prepared to this point, covered with a damp paper towel, and refrigerated for up to two hours.
When ready to eat, toss the salad lightly with the vinaigrette. Top with crumbled goat cheese and candied walnuts. As an option, you may plate the tossed salad and top individual portions with the cheese and nuts.