"Can you tell me what this is?"
"Yeah, but what's in it?"
"I don't know, I didn't make it."
Not the most informative shopkeeper, but in other respects, I found an excellent Thai shop today near Earls Court - Muay (8a Hogarth Road SW5 0PT). It's tiny but crammed full of essential Thai ingredients, even things like Marian plums (which look and taste like tiny yellow mangoes) and dry butterfly pea flowers, which I never managed to find in Chinatown.
I bought this dessert and eventually worked out that it's called Khanom Thua Pab - rice flour pancakes stuffed with fresh coconut and mung beans, served with a mix of sugar, salt and sesame seeds. The pancakes themselves aren't sweet at all, hence the generous bag of sugar/salt/sesame in the box, for seasoning to taste.
After I left Muay, I noticed another shop across the road - Manila Supermarket (11-12 Hogarth Road SW5 0QT). They sell even more home-cooked desserts, such as cassava cake, leche flan and fresh ube halaya, as well as savoury dishes and a big range of ingredients for Filipino cooking. I'm surprised at how these two shops aren't more famous, or at least how it took me so long to find out about them!