Sort and rinse the peas, then quick soak them by boiling for 2 minutes, then letting them stand covered for 1 hour. Drain and rinse with cold water.
Melt the butter in a large Dutch oven over medium-high heat until bubbly. Add the onion and cook until soft, then add the garlic and cook until fragrant.
Add the canned tomatoes, meaty ham bone, chicken stock, black pepper, cayenne pepper, and crushed red pepper flakes. Bring to a boil, then cook covered over medium-low heat for 30 minutes, stirring occasionally.
Remove the ham bone. Let it cool and chop off the meat, reserving it for later.
Cook the peas for another 30 minutes, adding a little filtered water or chicken stock if they get too thick.
Stir in most of the chopped ham. Let rest for 10 to 15 minutes. Garnish with fresh chives and the remaining ham.
Serve warm with cornbread and collard greens.