Combine balsamic vinegar in a saucepan and bring to a gentle boil. Allow to simmer until reduced by half, then whisk in olive oil, Dijon mustard, honey, and minced garlic. Season with salt and pepper and set aside to cool.

Boil salted water in a large pot. Add trimmed asparagus and cook for 4-5 minutes until bright green and tender-crisp. Remove immediately.

Transfer cooked asparagus to an ice bath for about 10 seconds, then drain and pat dry.

In a mixing bowl, combine cooled asparagus, halved grape tomatoes, and chopped walnuts. Toss gently.

Drizzle balsamic vinaigrette over the salad and toss lightly.

Sprinkle crumbled feta cheese on top and give a gentle mix. Serve immediately.