The Erast rail first class line? Sorry ram, I dun eat dog.Now's still winter time. Take the MTR across Luo Hu to Shenzhen. Dog meat stew should still be aplenty available. You won't regret trying it. It's not available in HK.
The mixed beef soup is something like our mixed pork kway chup soup except without the kway. The best version in China (or even in the world) is available in Guangzhou, not HK. Take the GZ-KL (港九快车)express train to Guangzhou.