make the dressing:
Whisk all ingredients together. Set aside.
prepare the vegetables:
Wash and trim the asparagus. Remove the tough parts of the stem, usually about the lower third of each stalk.
Wash and trim the spring onions.
Find the prettiest serving platter you own (or borrowed). Arrange the asparagus and onions lengthwise on the platter. Drizzle the dressing over the vegetables.
Heat the grill until it's screaming hot. Now, an important part is coming up so please pay attention.
The vegetables will cook quickly. We don't want them to cook through because the asparagus will get mushy and the onions will get tough.
Start with the asparagus. Arrange it on the grill grates so it doesn't fall through. Sorry, I had to say that.
As soon as the asparagus starts to brown, no more than 3 minutes, gently flip it over and cook for about another minute.
Place the lightly cooked asparagus back in the same serving platter. There's dressing on the bottom of the platter and you want that to coat the vegetables.
Next, throw the onions on the grill and arrange them so they don't fall through the grates.
Cook for about one minute. Gently flip them over and cook for another 30 to 45 seconds.
Remove the onions and place on the platter with the asparagus and dressing.
Serve warm or room temperature.