Candied Walnut–Apple Salad with Lemon Vinaigrette

1/4 cup of white sugar
2 tablespoons water
1/2 cup walnut halves
1 lemon
1/2 teaspoon Dijon mustard
1/2 clove garlic, finely minced
1/2 cup olive oil
Salt and pepper to taste
6 cups baby arugula leaves
2 Granny Smith apples, cored, seeded, and thinly sliced
2 tablespoons finely diced red onions
1/2 cup crumbled blue cheese

In a small saucepan over medium heat, combine the sugar and water; stir to completely dissolve the sugar. Cook for about 10 minutes, until the mixture is golden brown. Remove from the heat. Using a wooden spoon, stir in the nuts. Pour the nuts onto a parchment-lined sheet pan and spread them out. Let cool for 15 minutes, then chop into small pieces.

Use a microplane to zest half of the lemon into a small bowl. Add all of the lemon’s juice, then whisk in the Dijon mustard and garlic. Slowly pour in the olive oil, whisking constantly. Add salt and pepper to taste.
 
To serve, divide the arugula among 4 plates. Arrange the apples on top of the arugula. Spoon some diced onions over the apples. Sprinkle with the candied walnuts and blue cheese. Finish with a drizzle of vinaigrette.