Cut sprouts in half lengthwise through the stem. Use a sharp knife of mandolin and finely slice sprouts crosswise. Discard stems.
Coarsely chop spinach.
Add both spinach and Brussels sprouts to a large salad bowl.
Toast pecans in a dry saute pan over medium heat for a few minutes until you can smell them. Turn off heat and add to salad bowl along with the rest of ingredients.
Whisk the dressing ingredients together and toss with the salad right before serving.