There was a massive crowd gathered around this stall and there was even a policeman whose job seemed solely to keep the crowd from spilling out in to the road too far. There's a system where customers have to write their order (in Thai) on little numbered pieces of paper. There are multiple types of toast/bread but I didn't really know what to do, so I asked one of the staff members and he did my order there and then. I seemed to have accidentally pushed in ahead of dozens of people but maybe that wasn't the case. Either way, I got 'sangkaya' (an orange coconut/sugary/buttery/custardy option), peanut and chocolate. All three were tasty and they only cost 18B each. They're crispy/toasted on the outside and soft/spongey on the inside. Yum!
Mark Wiens says "For dessert we had Khanom Pang Jao Gao (ขนมปังเจ้าเก่าเด็ดในเยาวราช), an incredibly popular place that specializes in grilled bread"
Update: I definitely did skip the queue. I went back another evening and had to wait for at least 30 minutes. Write your order (in English is fine) on the paper and add it to the pile. Make sure you remember your number. It helps if you can understand Thai numbers. It was quite useful for practising my numbers.