Les cuisses de grenouilles literally means 'frogs' thighs'.  They can be prepared in many different ways.

Les cuisses de grenouilles à la provençale are frogs' legs prepared in the cooking-style of the area of Provence.   They are coated in flour, then lightly pan-fried in olive oil with the addition of melted butter, chopped garlic, chopped parsley and chopped baby tomatoes.