Clean the green beans. Snap off the ends, and slice them into bite-sized pieces. Set aside.
Starting with a large dry skillet, over medium heat. Spread the almonds in a single layer. Shake and stir the almonds constantly until the almonds are golden and fragrant, about 5 minutes.*
Add 2 tablespoons of butter and the olive oil into a large skillet over medium heat. Add the sliced mushrooms and green beans. Saute, stirring occasionally for about 15 minutes. The green beans should be bright green and tender.
Season with salt and pepper. Mix to combine.
Place the sauteed beans into a large casserole dish, and dot with the remaining butter. Finish the casserole with a squeeze of lemon or lemon zest. Sprinkle the toasted almonds over the top beans. Cover with aluminum foil until ready to serve.
Notes
*When the almonds are toasted remove from the pan immediately. Pour them onto a plate or bowl. If you keep them in the skillet they will continue to cook while the fry pan cools. They burn quickly!