Remove stems from kale and chop into bite-sized pieces. Place in a large salad bowl.
Drizzle 1 tablespoon olive oil over the kale and massage with your hands for 2-3 minutes until the leaves darken and become softer.
Trim brussels sprouts and shred them very thinly using a sharp knife or food processor. Add to the bowl with the massaged kale.
In a small bowl, whisk together 1 tablespoon olive oil, lemon juice, Dijon mustard (if using), salt and pepper until well combined.
Pour the dressing over the salad and toss thoroughly to coat all ingredients. Let sit for 5-10 minutes to allow flavors to develop.
Sprinkle with toasted pumpkin seeds and any optional add-ins you choose just before serving.