Preheat the oven to 225°F (100°C). Line a baking sheet with parchment paper.
Add egg whites and lemon juice to a clean mixing bowl. Beat with a mixer or with a stand mixer using a whisk attachment at medium speed until the egg whites are foamy.
Gradually add sugar, a tablespoon at a time, while mixing constantly with the mixer at medium-high speed. After all the sugar has been added mix the meringue at high speed for 1-2 minutes. Check if all the sugar is dissolved - rub a small amount of meringue between your fingers, you should not feel gritty (if it does feel gritty, just beat it a little bit longer, until it's smooth). The meringue should hold its shape (should form stiff peaks) and be stiff and glossy. The whole process of making meringue will take about 5-10 minutes.
Transfer meringue to a piping bag fitted with a large round tip (you can also use a disposable decorating bag or gallon-sized resealable plastic bag with a 1/2-inch hole cut in the bottom corner).
Pipe ghosts onto the parchment paper.
Attach candy eyes or miniature chocolate chips (if using). If not using candy eyes/choc chips, you can paint the eyes and mouth with a food coloring pen/melted chocolate after the meringue is baked.
Bake for 1 hour or until the ghosts are firm and dry to the touch. Turn off the oven and let the ghosts stay in the oven for one more hour, until completely dried. Open the door and let the ghosts dry for at least one hour or longer (even overnight).
Take the ghosts out of the oven and paint the eyes and mouths with a food coloring pen/melted chocolate (if not using candy eyes/miniature chocolate chips).
Enjoy!