Preheat the oven to 425 degrees Fahrenheit. Line a large, rimmed baking sheet with parchment paper for easy cleanup. To prepare the sweet potatoes, transfer them to the prepared baking sheet and toss them with 2 tablespoons olive oil. Sprinkle with salt and pepper and arrange in a single layer. Bake for 10 minutes, then toss and bake for 10 to 15 minutes longer, until tender and browning. Set the pan aside to cool. Meanwhile, combine the rinsed quinoa and broth in a medium saucepan. Bring the mixture to a boil over medium-high heat, then decrease the heat to maintain a simmer, cover, and cook until the quinoa has absorbed all the liquid, about 20 minutes. Fluff the quinoa with a fork and set aside to cool. To make the vinaigrette, combine all of the ingredients in a blender or food processor and process until mostly smooth, but with small pieces of herbs still visible. Transfer the chopped kale to a large serving bowl. Sprinkle with a dash of salt and then use your hands to “massage” the kale, grabbing big handfuls at a time and gently squeezing them in your fist until the kale is darker in color and more fragrant, about 15 seconds. Add the sweet potatoes, quinoa, kale, sunflower seeds and sliced basil to the bowl. Drizzle with about ⅓ cup dressing and gently toss until all of the ingredients are evenly coated. Taste and mix in more dressing if desired (you may want to use all of it). Serve the salad at room temperature or cold. Leftovers will keep well in the refrigerator, covered, for up to 2 days.