Step 1: In a medium bowl, combine the mixed dried fruits with 1/2 cup of brandy or rum. Stir well, cover, and let soak for at least 24 hours at room temperature, or up to a week in the refrigerator, stirring occasionally. Drain any excess liquid before use.
Step 2: Preheat your oven to 300°F (150°C). Grease and flour a 9x5 inch loaf pan, or line with parchment paper, leaving an overhang on the long sides for easy removal.
Step 3: In a medium bowl, whisk together the all-purpose flour, cinnamon, nutmeg, cloves, and salt. Set aside.
Step 4: In a large bowl, cream together the softened butter, brown sugar, and granulated sugar with an electric mixer until light and fluffy (about 3-5 minutes).
Step 5: Beat in the eggs one at a time, incorporating each egg fully before adding the next. Scrape down the sides of the bowl as needed.
Step 6: Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the dry ingredients. Mix on low speed just until combined; do not overmix.
Step 7: Gently fold in the drained, soaked fruits and chopped pecans or walnuts (if using) until evenly distributed throughout the batter.
Step 8: Pour the batter into the prepared loaf pan and spread evenly. Bake for 2 hours and 30 minutes, or until a wooden skewer inserted into the center comes out clean. If the top browns too quickly, tent loosely with aluminum foil.
Step 9: Once baked, remove the fruitcake from the oven and let it cool in the pan for 15 minutes before inverting it onto a wire rack to cool completely. While still warm, you can brush the top and sides with 1-2 tablespoons of additional brandy or rum.
Step 10: To make the buttery glaze, melt 1/4 cup of unsalted butter in a small saucepan over low heat. Remove from heat and whisk in the powdered sugar and 1 tablespoon of milk or brandy until smooth. Add more milk/brandy a teaspoon at a time if a thinner consistency is desired.
Step 11: Once the fruitcake has cooled for at least an hour (or is completely cool), pour the warm buttery glaze over the top, letting it drip down the sides. Allow the glaze to set before slicing and serving. For best flavor, store the fruitcake tightly wrapped and let it age for a few days or even weeks, periodically feeding it with a spoonful of brandy or rum.