Bring a large pot of HEAVILY salted water to boil. Add Potatoes to water and boil until barely fork tender. (No more than 20 minutes.) Drain and set aside to cool slightly.
Sauté Onions and Peppers in 2 T. of Butter on medium high heat until soft and slightly browned.
Sauté Mushrooms in 2 T. Butter on medium high until browned. (You can combine Onions, Peppers & Mushrooms and sauté together in 4 T. Butter to save a step, but the mushrooms release a lot of liquid and don't brown up as much as I like when cooked together.)
Mix Potatoes, Onions, Peppers & Mushrooms together. Add Garlic, Dill, Cajun Seasoning & Ground Pepper. Set aside.
Preheat Oven to 425
Add Vegetable Oil to frying pan and heat until smoking hot over high heat. Add Potato mixture. Do not stir hardly at all (only to keep from burning). You want as much crisp crust on the taters as you can get.
After crisped up, spread in a 9x13 baking dish and bake uncovered for 15 minutes.
While potatoes are in oven, in a small sauce pan melt 1 Stick of butter. Add 1 T. Garlic, 3/4 tsp Cajun Seasoning, Parsley and Ground Pepper to taste. Stir well.
When potatoes come out of oven, drizzle with seasoned butter and serve.