Well, this time around, I found a couple other recipes, including this one, which references both Nguyen's and Steamy Kitchen's (which also is based on Nguyen's) to look at, and did things slightly differently. As mentioned above, of course, I used a pressure cooker instead of the stove, which sped things up. The other big thing, though, was that I used my broiler to char the onions and ginger instead of a gas flame. This was much more convenient to do and very effective in getting a thorough char. By using a baking sheet/pan and broiler, you don't have to individually hold and turn each piece of onion and ginger. Actually, I no longer have a gas stove/oven, but the electric's been working just fine, and better yet, I actually have a broiler now, which has been very useful.
Lovely! Charred onions and ginger smell amazing.
Look at that beautiful color.
*UPDATE: It wasn't more richness I was missing! I was forgetting to add the sliced onions for the final broth, which is critical in rounding out the flavor. Don't omit the onion!