Cut green beans in half if you like pieces to be a little smaller.

Blanch the green beans: drop them into lightly salted boiling water and allow green beans to cook for about 3 to 4 minutes. Remove them from the boiling water with a slotted spoon and immediately plunge them into a bowl of ice cold water to stop the cooking process. Drain beans once they’re cool and set aside.

Add bacon pieces to a skillet over medium heat. Cook bacon for two minutes, then add diced onion and garlic and continue cooking for 3 to 5 minutes, or until bacon is done (but not crisp) and onions are golden brown. Remove from heat and set aside.

In a separate skillet or saucepan, melt butter over medium heat. Sprinkle flour into the pan and whisk immediately to evenly mix it into the butter. Cook for a minute or two, then pour in milk and half and half. Continue cooking, whisking constantly, while sauce thickens, about 2 minutes. Add salt, pepper, and cayenne then add the grated cheddar. Stir while cheese melts. Turn off heat.

Add pimentos to pan, then add bacon/onion mixture. Stir to combine. Pour over green beans and stir gently to combine. Pour into a baking dish and top with panko crumbs.

Bake at 350 degrees for 30 minutes or until sauce is bubbly and panko crumbs are golden.