Start by washing and trimming the ends off your green beans. Bring a large pot of salted water to a rolling boil, then drop the beans in. Let them cook for about 2 to 3 minutes until they turn bright green and are just barely tender.
As soon as the beans are done boiling, drain them and plunge them straight into a bowl of ice water. This stops the cooking process immediately and keeps the beans crisp instead of mushy. Let them sit for a minute, then drain again and pat them dry.
Heat a skillet over medium heat and add the sliced almonds without any oil or butter yet. Stir them often so they don't burn, cooking for about 3 to 4 minutes until golden brown. Remove them from the pan right away and set them aside on a plate.
In the same skillet, melt the butter over medium heat. Add the minced shallots and cook for 2 to 3 minutes until they soften and turn translucent. Stir in the garlic during the last 30 seconds so it doesn't burn or turn bitter.
Toss the blanched green beans into the skillet with the shallots and garlic. Cook everything together for 3 to 4 minutes, stirring often so the beans soak up all that buttery flavor. You want them warmed through but still a little crisp.
Remove the pan from the heat and stir in the lemon juice and lemon zest. Season generously with salt and pepper, then fold in most of the toasted almonds. Transfer everything to a serving dish and top with the remaining almonds and parsley.