Heat butter and oil over medium-high heat in a large, shallow pan.
Add beans and cook, stirring, for about 4 minutes. Add garlic and pepper flakes, if using, and stir.
Add water and cover. Cook for 3 to 5 minutes, depending on desired doneness (for crisp-tender 3-4 minutes is good).
Remove lid and, turning heat to high, cook stirring constantly until liquid evaporates and some beans start to brown and char.
Add salt and pepper to taste and serve immediately.
Grill method:
Trim and cut beans.
Coat beans with only olive oil (no butter) and toss with garlic, salt and pepper, and red pepper flakes, if using.
Using a high-sided grill pan with holes, grill the beans over medium-high heat for about 10 minutes or until done, tossing frequently. Make sure to let some of the beans get a little charred on them…oh SO good.
Notes
*To Use Frozen Beans: Adjust cooking times by cooking 5-8 minutes before adding the garlic and water, testing the beans after covering at about the 4 minute mark. Cook without lid until desired doneness. (To grill frozen beans, follow the steps above, adding another 1-2 minutes or until the beans are starting to char.)