Preheat oven to 400 degrees (205 C.)
Wash potatoes, cut in similar sizes, some will be halved, some quartered.
Season with salt and pepper.
Mix chopped garlic with mustard. Add thyme, panko breadcrumbs and olive oil as needed. I used a pestle and mortar.
The breadcrumbs will not evenly coat the potatoes and that is what you want. Just a little crunch. (OR you can skip).
Bake on baking sheet, cast iron griddle or baking stone.
After baking 20 minutes, turn potatoes, add mushrooms and reduce oven to 375 F. (190 C.)
Bake another 15 or 20 minutes until golden brown.
Add olives in the last 10 minutes. When you remove from oven, squeeze lemon over potatoes. Season with more salt and pepper if needed.