Blanch the fresh green beans by adding them to salted boiling water and cooking for 5 minutes. Drain immediately and transfer to a bowl of ice water to stop the cooking. Once cooled, drain again and set aside. If using frozen green beans, thaw them in a colander under cold running water (or leave them in the fridge overnight). Drain well and pat dry with a clean towel to remove excess moisture. Set aside.
In a mixing bowl, combine low-fat plain Greek yogurt with dried tarragon, dried oregano, ground rosemary, parsley flakes, dried basil, salt, and pepper. Taste and adjust the salt if needed.
Add grated cheese to the Greek yogurt mixture, and mix it.
Whisk all-purpose flour into the Greek yogurt mixture until smooth and combined.
Toss the green beans with the yogurt mixture, then transfer everything to a baking dish.
Cover the dish with aluminum foil and bake for 25 minutes.
Remove the foil, sprinkle plain Panko breadcrumbs evenly over the top, and set your oven to broil.
Broil until the topping is golden. Keep a close eye on it to avoid burning, because it will be done in a few minutes.
Amount of plain panko breadcrumbs: it all depends on the size of your baking dish. If the surface is large, you might need more breadcrumbs, or if the surface is smaller you might need less breadcrumbs. Avoid putting too many breadcrumbs.
If your yogurt is very thick, add 1–2 tablespoons of lactose-free milk or water to thin the sauce slightly so it coats the beans evenly.
Low FODMAP: Substitute all-purpose flour with starch, and use lactose-free plain Greek yogurt. For topping ideas, see the section above on topping substitutes.
Gallbladder diet: use low-fat semi hard cheese, or fresh mozzarella.