01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners or grease thoroughly.
02 - In a large bowl, whisk together whole milk, heavy cream, eggs, granulated sugar, brown sugar, vanilla extract, and salt until fully combined.
03 - Add bread cubes to the custard mixture and fold gently to coat. Let sit for 10 minutes so bread absorbs liquid.
04 - In a small bowl, toss diced apples with lemon juice and cinnamon until evenly coated.
05 - Fold the prepared apples and half the caramel sauce into the soaked bread mixture. If using, add chopped nuts and combine gently.
06 - Divide mixture evenly among muffin cups, filling each to the top. Drizzle remaining caramel over each portion.
07 - In a small bowl, mix topping brown sugar and cinnamon. Sprinkle mixture over the muffins.
08 - Bake for 28 to 32 minutes, until muffins are golden brown and set in the center.
09 - Allow muffins to cool in the tin for 10 minutes, then transfer to a wire rack. Drizzle additional caramel over the top before serving, if desired.