Slice the tops of your peppers off and de-seed. Steam the tops and bases of the peppers in a pot for about 7 minutes. Remove and allow them to drain.
Heat the oil in a large skillet. Add in the scallions and sauté for 2-3 minutes on medium. Fold in the spinach and semi-wilt. Stir in the parsley, dill and garlic for 30 seconds and season with salt and pepper to taste. Remove the mixture from heat.
In a large bowl, mix together the cheeses, breadcrumbs and egg. Add the spinach mixture to the bowl and combine. Stuff each pepper with this mixture, place in a small casserole dish and place tops back on. Drizzle with olive oil, cover with foil and bake for 30 minutes. Uncover and bake for 15 minutes. Pepper should be fork tender.
Notes
When salting the spinach, also keep in mind that the feta cheese has a salty taste.