When To Use Milk Vs. Heavy Cream In An Egg Wash
For a baker, an egg wash works like an Instagram filter for pastries and bread: what was once pale and dull is now golden and glossy. Simple in ingredients and execution, a blend of egg, water or dairy, and salt can be brushed onto any baked good to immediately enhance the appearance of the crust. Still, even with this basic formula, there can be a range of results depending on what liquid you use.
This is especially true for what kind of dairy you opt for. While the high fat of the golden egg yolk of the egg wash helps improve the color, the dairy helps give your bread a boost of shine. How shiny? Well, it depends on the dairy. Whole milk, a traditional option, imparts good shine, enough for a standard reflective sheen. But when you up the richness, going from milk to heavy cream, the gloss goes into overdrive, and the color goes even darker, resembling an edible lacquer.
Why? The proteins and sugars in both milk and heavy cream help increase the shine of the egg wash, but the added fat in the heavy cream contributes to the crust's browning. So when should you reach for the heavy cream and whole milk? It should be determined by the level of gloss you desire and how dark you want your crust to go.
The richer the dairy, the brighter the shine
Some bread requires a little extra shine and golden hue, like bubble-topped brioche or butter-rich dinner rolls. For these special recipes, reach for heavy cream, as that boost in shine and color will reward you with a stunning exterior. But where shininess isn't the most important point of the egg wash, i.e., color is the primary use, like for standard white bread, biscuits, or even peanut butter cookies, use whole milk instead.
Furthermore, if you're just using egg wash to seal your hand pies or other pastries, you can skip the dairy altogether and thin out your egg wash with water, as no shine or color is needed when using it an edible glue. Keep in mind that adding rich dairy increases the browning on the top of your baked goods, so you may need to tent with foil after the first 20 minutes of baking.
As for the amounts, the formula is pretty straightforward: add one tablespoon of either milk or heavy cream to one beaten egg. From there, you can see for yourself how one egg wash can outshine another.