First Step: Prep Your Ingredients and Oven
Start by preheating your oven to 350°F (175-180°C). Line baking sheets with parchment paper to prevent sticking and to help achieve an even bake. Make sure your unsalted butter is softened to room temperature, and any eggs are rested outside the fridge to avoid curdling when mixed.

Second Step: Cream the Butter and Sugar
In a large mixing bowl, beat the softened butter together with granulated or powdered sugar until the mixture becomes light and fluffy. This takes about 2-5 minutes depending on whether you use an electric mixer or whisk by hand. The creaming step is key for incorporating air that impacts final texture.

Third Step: Add Egg and Vanilla
Beat in the whole egg and 4 teaspoons of vanilla extract slowly, ensuring everything is well combined. If you want a lighter and crisper wafer, gently fold in the optional 3 egg whites now and mix until smooth.

Fourth Step: Combine Dry Ingredients
In a separate bowl, whisk together 1 ½ to 1 ¾ cups of all-purpose flour, ¾ teaspoon baking powder, and ½ teaspoon salt (adjust if using salted butter). This ensures even distribution and prevents lumps in the dough.

Fifth Step: Incorporate Dry Ingredients and Milk
Gradually add half the dry ingredients to the wet mixture, stirring on a low speed to avoid overmixing. Add 1 tablespoon of whole milk or ¼ cup heavy cream and gently mix again, adding remaining dry ingredients last. Mix just until you get a thick, batter-like dough.

Sixth Step: Pipe and Shape the Wafers
Transfer your dough to a piping bag fitted with a medium plain tip or a ziplock bag with a corner snipped off. Pipe small mounds about 2 teaspoons each or roughly 1 inch in diameter, spaced 1½ to 2 inches apart on the baking sheet. Lightly flatten each mound with damp fingers for even spreading and crisp edges.

Seventh Step: Bake to Perfection
Bake for 12 to 20 minutes depending on your oven and wafer thickness. Rotate the baking sheets halfway through to ensure even browning. Watch for light golden edges, which indicate they are done. Baking too long will make the wafers too brittle.

Final Step: Cooling and Serving
Allow vanilla wafers to cool on the baking sheet for 5 to 10 minutes before transferring them to a wire rack to cool completely. This cooling process helps the wafers set with the perfect crisp texture. Serve as a snack, pair with desserts like banana pudding, or use as a crust base for creative recipes.