Heat oven to 350 degrees. In a bowl, mix bread crumbs with the oregano and zest. Pour 1/4-cup olive oil onto a cookie sheet, followed by the breadcrum mixture. Mix well. Toast it in the oven, tossing frequently, until golden brown, 10 to 12 minutes.

Heat butter and remaining olive oil in a large skillet over medium-high heat
until foamy. Add the Brussels sprouts cut side down, sprinkle with salt and
pepper, and sauté, until bottoms lightly browned, about 5 minutes. Work in
batches until all the sprouts are browned removing them to a plate when finished

Leaving any liquids in the pan add the diced pancetta, and sauté, tossing
frequently, until they begin to brown.

Return all the sprouts to the pan and cook over medium high heat until well
browned and softened slightly, about 8 minutes more. The pancetta will be crisp.
Reduce heat; add red onion and garlic, and sauté until fragrant, 2 minutes.

Increase heat to high, add balsamic vinegar and stock, and cook, tossing
frequently, until sprouts are glazed and tender, about 10 minutes; add more stock
if needed. Taste, adjusting seasoning if necessary, and sprinkle with chopped
parsley. Transfer to a warm serving bowl and scatter breadcrumbs on top.