Melt the butter in a large pot on the stove over medium heat. Add the onions and saute for 5 minutes.
Add potatoes, stock, and herbs to the pot. Turn up the heat until the liquid nearly boils, then turn down to a lively simmer. Cover and let simmer until the potatoes are soft, about 20-25 minutes.
If you plan to serve the soup with bacon, cook the bacon now while the potatoes soften.
When the potatoes are soft, add clams (with their liquid), clam juice, milk, cream, and corn. Heat through.
Add salt and pepper to taste. Serve with crumbled bacon, if desired.