Preheat oven to 375 degrees F. Bring a pot of water (with 1/2 tsp salt) to a boil.
Add beans to boiling water and blanch for 5 minutes. While beans are boiling create an ice bath in a large bowl. Once 5 minutes have passed, drain beans in colander and plunge in ice bath. The ice bath prevents the beans from turning to mush, by stopping the cooking process. Drain again in colander and set to the side.
In a skillet, melt butter and heat olive oil on medium-high heat setting. Add onion and sautee until translucent. Add minced garlic and sautee until fragrant. Add salt and pepper and cook for another minute.
Sprinkle all-purpose flour onto onion & garlic mixture and stir together for 1 minute. Whisk in chicken broth, making sure mixture is lump-free. Whisk in half-and-half. Cook until the mixture has thickened, stirring occasionally (at a simmer) for 5-6 minutes.
Pour sauce over bowl of beans and toss to combine. Transfer to your chosen dish and sprinkle with breadcrumbs, french fried onions, salt & pepper.
Bake for 20 minutes or until bubbly. Keep an eye on the dish, as it may brown quickly. Simply cover with foil to avoid burning toppings.