Prep your oven and pans: Heat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats.

Whisk the dry ingredients: In a bowl, whisk 1 1/2 cups all-purpose flour, 1 teaspoon baking soda, 1 teaspoon ground cinnamon, 1/4 teaspoon nutmeg, 1/2 teaspoon fine salt, and 1 tablespoon cornstarch (if using). Stir in 2 cups rolled oats. Set aside.

Cream the butter and sugars: In a large bowl, beat 1/2 cup softened unsalted butter with 3/4 cup brown sugar and 1/4 cup granulated sugar until light and fluffy, about 2 minutes.

Add eggs and vanilla: Beat in 1 large egg and 1 1/2 teaspoons vanilla extract until smooth and creamy.

Combine wet and dry: Add the dry mixture to the butter mixture. Mix on low until just combined. Do not overmix.

Prep the apple: Peel (optional), core, and finely dice 1 medium apple into small pea-sized pieces. Toss with 1 teaspoon lemon juice if you like to prevent browning.

Fold in the mix-ins: Stir in the diced apple and 3/4 to 1 cup caramel bits or chopped soft caramels. The dough should be thick and scoopable.

Scoop the dough: Use a medium cookie scoop (about 1 1/2 tablespoons) to drop balls onto prepared sheets, spacing 2 inches apart. If any large caramel pieces are on the bottom of a dough ball, nudge them to the top or sides to reduce sticking.

Bake: Bake 9–11 minutes, until edges are set and lightly golden but centers still look a touch soft. Rotate the pans halfway for even baking.

Cool: Let cookies rest on the sheet for 5 minutes. Slide the parchment onto a cooling rack and cool completely. If any caramel oozes, gently loosen with a thin spatula while still warm.

Optional finish: Sprinkle a tiny pinch of flaky sea salt on warm cookies for a sweet-salty pop.