In a large non-stick skillet over medium-high heat, heat the oil until shimmering. Add the mushrooms, garlic, herbes, salt and pepper to taste. Stir well to combine.
Cook over medium heat until the mushrooms give up their liquid and the liquid starts to evaporate. Stir frequently to prevent burning. Once the mushrooms are golden brown, remove from heat. Adjust seasonings and serve.
Whole mushrooms will always be a bit cheaper (unless sliced is on sale) then the sliced variety. So buy whole mushrooms and slice them yourselves to save a few pennies.
The mushrooms will release quite a bit of liquid as they cook. As they do, they will begin to caramelize and develop that beautiful deep brown color.
You can use button mushrooms or baby portabella mushrooms for these. Again, generally button mushrooms will be a bit on the cheaper side, so that's we generally use.