Tucked away in a narrow alleyway, this San Francisco institution has been dishing up bamboo steamers of dim sum for more than a century. First opened in 1920, it bears the distinction of being the oldest dim sum restaurant in the United States. Although the prices have inched up ever so slightly—back in the 1930s, a basket of ha gow went for a mere $0.30—the menu of Cantonese stalwarts has remained largely the same for decades. Customers today can still fuel up on crispy potstickers, char siu bao, chicken feet…