1½ tsp. sugar
¾ tsp. kosher salt
1⅓ cups (180 g) all-purpose flour, plus more for surface
¾ cup (1½ sticks) chilled unsalted butter
FILLING AND ASSEMBLY
2 tsp. fennel seeds (optional)
1 tsp. kosher salt
⅓ cup sugar, plus more for sprinkling
2 lb. apples (such as Pink Lady, Honeycrisp, or Granny Smith), scrubbed, cored, thinly sliced
1 Tbsp. apple cider vinegar
1 tsp. vanilla extract
1Tbsp. heavy cream
Softly whipped cream or vanilla ice cream (for serving; optional)
A spice mill or mortar and pestle
Whisk sugar, salt, and 1⅓ cups flour in a medium bowl. Cut butter into 6 rectangular pieces (if using ½-cup sticks, cut them in half crosswise, then in half again lengthwise). Toss butter in dry ingredients to coat, then dump mixture out onto a work surface. Most recipes start by pulverizing fat into small bits, but here you’ll use a rolling pin to flatten flour-coated butter into sheets that will puff into layers when baked.
Roll butter into flour until it is in long flexible strips, using a bench scraper to scrape butter off rolling pin or surface as needed.
Use bench scraper to gather mixture into a loose pile, then drizzle 4 Tbsp. ice water over.
Using your hands and the bench scraper, toss mixture until water is distributed, then gather into a rectangular pile.
Roll out dough to a long rectangle with short ends about 8" wide, then use bench scraper to fold dough into thirds, like folding a letter. It will be very crumbly and loose; don’t panic. This turns the floury mass into a cohesive unit while creating flaky-making stacks of fat and flour.
Using bench scraper to help, turn rectangle 90° and repeat rolling and folding, gathering loose bits of dough from outer edges into the center and flouring surface as needed.
Repeat rolling and folding a third time. Dough should be somewhat homogenous and creamy-looking with some dry bits around edges. Squeeze a bit in your palm; it should loosely hold together. If not, repeat rolling and folding.
Wrap folded dough in plastic, then press it into a compact disk about 1" thick. Chill 30 minutes.
Roll out dough on a lightly floured surface to a 12"–14" round or oval about ⅛" thick (don’t worry about cracks around perimeter). Dust surface and rolling pin with flour as needed and rotate dough often to prevent wider cracks. If dough sticks to surface, lift on one side and scatter flour underneath before continuing. Roll dough onto your pin, then unfurl it on a sheet of parchment paper. Slide onto a rimmed baking sheet and chill while you prep the filling.
Do Ahead: Dough can be made 3 days ahead. Keep chilled, or transfer to a resealable plastic bag and freeze up to 3 months. Thaw overnight in the refrigerator before rolling out.
FILLING AND ASSEMBLY
Preheat oven to 400°. 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 ⅓ cup sugar. Toss with your hands to combine, then add apples and toss to coat. Add vinegar and vanilla; toss gently.
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.
Place galette in oven and immediately reduce heat to 375°. 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.
Serve galette with whipped cream or ice cream if desired.