01 - Preheat the oven to 375°F. Line a 12-cup muffin tin with paper liners or lightly grease each cup.
02 - In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, ground cinnamon, and ground nutmeg until evenly blended.
03 - In a separate bowl, whisk the melted unsalted butter, light brown sugar, granulated sugar, eggs, and vanilla extract until smooth. Stir in the whole milk.
04 - Add the wet mixture to the dry ingredients and gently stir just until combined. Avoid overmixing to ensure tender muffins.
05 - Fold the diced apples and chopped caramel candies into the batter, or swirl in dollops of caramel sauce according to preference.
06 - Divide the batter evenly among the prepared muffin cups, filling each approximately three-quarters full.
07 - Sprinkle each muffin with coarse sugar and chopped nuts if using.
08 - Place muffin tin in oven and bake for 20 to 22 minutes until tops are golden and a toothpick inserted in the center emerges clean, avoiding caramel pockets.
09 - Let baked muffins cool in the tin for 5 minutes, then transfer them to a wire rack to cool completely.