Trim, cut green beans in half then boil for 5 minutes then shock in ice water and strain. Set aside.
Melt butter over medium heat and cook onion for 10 minutes. Stirring occasionally.
Add minced garlic and cook for 2 minutes.
Stir in flour and cook 2 minutes more.
Pour in white wine, whisk and cook for one minute.
Add chicken stock and turn heat up and allow to thicken while whisking.
Whisk in heavy whipping cream, salt, pepper, and boursin cheese. Whisk until fully incorporated and the cheese has melted.
Add green beans to a baking pan and pour the sauce over the green beans. Mix well then bake covered at 375 for one hour. Remove from the oven, stir and top with fried onions.