Prepare the Strawberries: In a medium bowl, combine the sliced strawberries and sugar. Gently toss the strawberries to coat them evenly in the sugar. Set them aside for about 5 minutes to allow the sugar to draw out the natural juices from the strawberries.
Make the Dressing: In a large salad bowl, whisk together the olive oil, balsamic vinegar, water, Dijon mustard, salt, and pepper. Continue whisking until the dressing is creamy and emulsified. Taste the dressing and adjust seasoning as needed. Set it aside.
Toast the Nuts or Seeds: Heat a pan over medium heat and toast your choice of nuts or seeds. Keep an eye on them as they can burn quickly. Once they are lightly charred, remove them from the heat and set them aside to cool.
Massage the Kale: Pour the dressing over the fresh baby kale. Using your hands, gently massage the kale leaves until they are evenly coated with the dressing. This process softens the kale and reduces the bitterness.
Assemble the Salad: Add half of the strawberries and toasted nuts or seeds to the kale and toss everything together. Top the salad with the remaining strawberries, nuts, and seeds.
Serve and Enjoy: Serve the salad immediately for the best flavor and texture. If you're planning to transport or save it, wait until just before serving to add the dressing and toss everything together.