Preheat oven to 325°F (165°C).

Place pecans on small rimmed baking sheet.

Bake nuts until toasted—about 5–10 minutes (be careful not to burn!)

Meanwhile, in a large sauté pan, cook bacon over mediumhigh heat until crispy.

Drain on paper towels, and save the extra bacon fat for future use.

Whisk mustard, vinegar, and lemon juice in a small bowl; whisk in oil.

Season with pepper.

Using processor fitted with 1/8- to ¼-inch slicing disk, slice Brussels sprouts (alternately, you can slice with knife).

Transfer to large bowl.

Preheat large skillet over medium heat, and add in 1–2 tablespoons of the leftover bacon fat.

Add in Brussels sprouts and sauté until softened and slightly brown.

Pour the mustard/vinegar/lemon juice/olive oil mixture over the sprouts.

Mix in ½ the pecans, the bacon, and scallions.

Place slaw in a serving bowl and top with remaining pecans.