Pre heat oven to 375 degrees. In a medium size pan, bring 3 cups of water to a boil.
Rinse lentils, discard any pebbles or dirt. Add lentils to boiling water. Cook for 15 minutes until just cooked through. Rinse with cold water. Set aside.
In a large pan over medium high heat, add 1 TBSP of olive oil. Sauté garlic, chopped pepper tops and mushrooms for 4-5 minutes. Do not move the mushrooms much so that they carmelize. Add in seasonings- salt through paprika. Add in remaining vegetables and parsley reserving a few pieces for garnish. Sauté until just cooked through- about 5 minutes. Stir in cooked lentils.
Spoon lentil and vegetable mixture into peppers, crumbling in a small amount of feta as you go. Fill peppers to the top, add parmesan to each pepper and remaining feta. (see photos)
Drizzle with olive oil.
Set in a shallow roasting pan or oven proof dish.
Roast peppers at 375 for 15 minutes. Reduce heat to 350 and bake another 15 minutes or until peppers are soft and feta is golden brown. Remove carefully from pan with a spatula and a pair of tongs.