Step 1

Preparation Preheat oven to 400°F. Toast fennel seeds (if using) in a small dry skillet over medium-high heat until golden brown and fragrant, about 3 minutes. Let cool, then finely grind in spice mill or with mortar and pestle. Transfer to a medium bowl and add salt and 1/3 cup sugar. Toss with your hands to combine, then add apples and toss to coat. Add vinegar and vanilla; toss gently.

Step 2

Arrange apple mixture in the center of chilled dough (still on parchment on baking sheet) and spread out evenly, overlapping slices if desired and leaving a 3" border. Fold edges of dough up and over fruit, pleating as needed and being careful that folded edge of dough doesn’t tear (if it does, patch with dough scraps and pinch to seal). Pour cream into a small bowl and brush all over dough. Sprinkle sugar evenly over dough.

Step 3

Place galette in oven and immediately reduce heat to 375°F. Bake, rotating halfway through, until crust is deep golden brown everywhere, apples are softened, and juices are bubbling, 45–50 minutes. Let galette cool 2 hours.

Step 4

Serve galette with whipped cream or ice cream if desired.