1. Preheat your oven to 375°F. Line a muffin tin with paper liners or lightly grease with butter.
2. Peel and dice 1.5 to 2 cups of firm apples into small, bite-sized pieces. Toss them with a splash of lemon juice or a tablespoon of flour to prevent browning.
3. Prepare the streusel topping by mixing cold butter, flour, oats, chopped peanuts or pecans, brown sugar, and cinnamon. Blend until the mixture looks like coarse crumbs, then set aside.
4. Cream unsalted butter and both granulated and brown sugars together until fluffy using a hand or stand mixer on medium speed.
5. Add eggs one at a time to the butter-sugar mixture, ensuring each is fully mixed in before adding the next.
6. Mix in sour cream (or yogurt) and vanilla extract, blending until the batter becomes smooth.
7. In a separate bowl, combine dry ingredients: flour, baking powder, cinnamon, nutmeg, cloves, and a pinch of salt.
8. Gradually add the dry ingredients to the wet ingredients, folding them together gently. Avoid overmixing to keep the batter light and tender.
9. Fold in the diced apples carefully, distributing them evenly throughout the batter.
10. Spoon the batter into the prepared muffin tin, filling each liner about two-thirds full.
11. Generously sprinkle the peanut streusel topping over each muffin.
12. Bake the muffins in the preheated oven for 17-20 minutes or until a toothpick inserted in the center comes out clean.
13. Once baked, remove the muffins from the oven and let them cool slightly in the pan.
14. Drizzle warm caramel sauce over the cooled muffins to enhance the gooey, flavorful topping.
15. Let the muffins cool completely on a wire rack before serving or storing.

Enjoy your delicious Gooey Caramel Apple Muffins with Peanut Streusel warm or at room temperature!