Preheat oven to 425 degrees F.
Crack egg into a large bowl and lightly whisk. Add the lamb, breadcrumbs, shallot, garlic, lemon zest (zest only!), mint, parsley, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Using your hands, mix well. Form into 10 2-inch meatballs.
Coat a 10-inch ovenproof skillet with olive oil and place the meatballs on the skillet so that they are not touching. Bake for 10 minutes, then remove skillet from the oven, scoot the meatballs to the edge of the skillet, and add the couscous, butter, reserved lemon juice, and 1 cup of hot water (as hot as your sink will go!). Stir to coat the couscous in water, carefully scooting the meatballs around as you go. Cover the skillet with a fitted lid (or aluminum foil in a pinch) and return to the oven for 10 more minutes.
While the meatballs are cooking, make the whipped feta. Combine the feta, Greek yogurt, mint, parsley, extra-virgin olive oil, and lemon juice in a blender or food processor and blend until smooth. Taste and season with salt and pepper as needed (some feta is saltier than others—I didn’t need any salt at all).
Remove skillet from the oven and use a fork to carefully fluff the couscous all around the meatballs.
To build your plate, grab a heaping spoonful of whipped feta and swipe it across half of your plate. Add couscous and any vegetables you might be using, then top with the meatballs and more fresh herbs.