In a large bowl, toss the spinach with the cheese, pecans, and thinly sliced onion.
Heat the ghee oil in a small saucepan or skillet over medium heat for 2-3 minutes.
Once the ghee is warmed, remove the pan from the heat and whisk in the mustard, honey, and vinegar until emulsified.
Drizzle the warm dressing over the salad, toss to combine, and serve immediately.
*Optional - Garnish with additional shaved Parmesan Reggiano