Add all ingredients, except lettuce, to a mixing bowl and whisk to combine. Heat nonstick skillet to medium heat, add egg mixture and cook to desired consistency. Add cooked egg to the edge of lettuce leaf and fold over. Best if eaten immediately.: The aroma of the raw egg and the faint vegetal scent of the torn baby spinach mingle, and whisking aerates the mixture so the cooked curds are tender. Whisk until the color is uniform and you see small bubbles on the surface, that signals enough air incorporated for fluffiness. This matters because even mixing ensures each bite has the right balance of egg , spinach , and feta crumbles fat free . A common mistake is under whisking which leads to uneven texture, or over beating which can make the egg dense.
Heat nonstick skillet to medium heat: You will notice the pan warming and a faint metallic scent as it approaches medium temperature, which is ideal for gentle cooking. A properly warmed skillet prevents sticking and produces soft curds rather than browned, rubbery egg . I tap the pan lightly and then add a small amount of oil if needed, although the nonstick surface often suffices. Avoid using high heat, because that will cook the outside too quickly and leave the interior underdone.
Add egg mixture and cook to desired consistency: As the mixture hits the skillet you will hear a soft, delicate sizzle and see the edges set first, turning glossy then matte as they firm up. Using a silicone spatula, gently fold the setting egg toward the center so you get large, tender curds. The smell will deepen into a warm, savory note; watch for a slight color change to pale gold for a custardy result. This technique preserves moisture and creates creamy curds. A common problem is stirring too vigorously, which makes the egg break into tiny, dry pieces.
Add cooked egg to the edge of lettuce leaf and fold over: The cool crisp scent of the lettuce leaf large contrasts with the warm, eggy aroma as you transfer the filling. Place the soft egg mixture near one side so you can fold the leaf over like a taco, creating a pleasant textural contrast with every bite. The lettuce should remain crisp, so make sure it is dry before adding the filling. If you add the hot filling to a wet leaf, it will wilt quickly and lose the satisfying crunch.
Best if eaten immediately: Freshness is the final sensory flourish, with steam rising slightly from the warm filling and the lettuce offering a crisp snap. Eating right away preserves the contrast between warm interior and cool exterior, and keeps the lettuce leaf large from becoming soggy. I always recommend folding and eating within minutes, because storing can cause the leaf to soften and the filling to release moisture. Reheating tends to dry out the egg , so avoid attempting to prepare this far in advance.