Keep the garlic cloves whole. Quickly rinse the button mushrooms in water and pat them dry with a paper towel, then cut them in half.
In a pan, heat olive oil and add the garlic. Cook over low heat for 3-4 minutes, until the outside turns golden and the inside becomes tender.
When the garlic is cooked, add the mushrooms and stir-fry for 2-3 minutes until their moisture evaporates and they soften.
Right before turning off the heat, add a pinch of salt and a dash of black pepper.