Whisk powdered sugar, milk, and vanilla extract in a small bowl. Adjust consistency by adding milk, 1 teaspoon at a time, if needed.
7. Glaze & Serve
Drizzle glaze over slightly cooled apple slices. Let set for 10 minutes before cutting into squares and serving.
Tips for the Best Apple Slices
Use a Mix of Apples: Combine tart and sweet apples (e.g., Granny Smith + Honeycrisp) for the best flavor.
Chill the Dough: Keep butter cold and dough chilled for a flaky, tender crust.
Prevent a Soggy Bottom: Blind-bake the bottom crust for 10 minutes before adding the apple filling.
Serving Suggestion
Serve warm or at room temperature, optionally with a scoop of vanilla ice cream or a dollop of whipped cream for extra indulgence.
