A drizzle of maple syrup at the end adds just the right amount of sweetness.
Peel, core, and cut apple into 1-inch slices. Put apple, ginger, and 1/2 cup water into a small saucepan. Cover, and bring to a simmer over medium-high heat. Reduce heat to medium-low; cook, stirring occasionally, until apple is soft, about 10 minutes. Uncover; cook, stirring often, until apple has broken down and liquid has just evaporated, about 15 minutes. Press the mixture through a large-mesh sieve into a medium bowl. Let cool completely. Refrigerate until cold.
Put egg whites and salt into the bowl of an electric mixer fitted with the whisk attachment. Beat on medium speed until stiff peaks form. Add sugar, and beat on medium-high speed until glossy.
Gently fold 1/4 cup plus 2 tablespoons cold apple mixture into egg whites. Serve immediately, drizzled with syrup.
The eggs in this recipe are not cooked. It should not be prepared for pregnant women, babies, young children, the elderly, or anyone whose health is compromised. Apple mixture can be refrigerated in an airtight container up to 3 days.