Bring a large pot of salted water to a boil, then add the asparagus and cook for 3 to 5 minutes until it turns bright green and is crisp with just a little give when pierced with a fork. Right away, transfer the asparagus to a bowl filled with ice water — this stops the cooking immediately. Let it sit for a couple of minutes, then drain well and pat it dry with a clean kitchen towel.
In a small bowl, whisk together the olive oil, Dijon mustard, and maple syrup until the mixture is smooth and emulsified.
In a large bowl, toss together the blanched asparagus, mixed greens, cherry tomatoes, and red onion. Drizzle the vinaigrette over the top and gently toss everything to coat. Season with the kosher salt and ground black pepper.
Transfer the salad to a large serving bowl or divide it among individual plates. Scatter the crumbled goat cheese and walnuts over the top, and finish with an extra pinch of salt and a few cracks of fresh black pepper if you like.