Spinach and radiccio salad with mushrooms and cashews

2 tablespoons fresh lemon juice
2 tablespoons balsamic vinegar
2 teaspoons country-style Dijon mustard
1/2 cup extra-virgin olive oil
1 6-ounce bag fresh baby spinach
1 head radicchio, torn into bite-size pieces
8 ounces button mushrooms, sliced
2 green onions, minced
1/2 cup chopped roasted cashews

Whisk first 3 ingredients in small bowl. Gradually whisk in oil. Season dressing to taste with salt and pepper. Combine spinach and all remaining ingredients in large bowl. Add dressing to taste; toss to coat.