Preheat the oven to 355°F (180°C).
Peel the sweet potato using a vegetable peeler into long, thin ribbons. Spread them on a parchment-lined baking sheet, mist lightly with cooking spray, and bake for 20 minutes, until crisp and lightly golden.
Meanwhile, toast the pecans in a dry skillet over medium heat for 4–5 minutes, shaking occasionally, until fragrant and golden. Remove from heat and let cool.
If desired, lightly scorch the Brie slices with a kitchen torch until just melted at the edges.
In a small bowl or jar, whisk together the lemon juice, mustard, garlic, honey or date syrup, olive oil, salt, and pepper until emulsified.
Arrange the romaine, arugula, raspberries, toasted pecans, crispy sweet potato, and Brie in a large bowl or serving platter. Drizzle with the dressing just before serving and toss gently to combine.