Preheat oven to 350 degrees F. Adjust rack to the center of the oven.
Prepare a 9" by 5" loaf pan by greasing bottom and sides with butter, olive oil or cooking spray. Or line it with parchment paper.
Grate the Parmigiano using a box grater with large holes. Divide grated cheese in half and sprinkle 1/2 of the grated cheese on the bottom of the pan.
In a large bowl, whisk the dry ingredients together. Add the cubed cheddar and toss to coat.
In a separate bowl, whisk the egg, milk, melted butter and sour cream together until well blended.
Fold the wet ingredients into the dry ingredients, mixing just until combined, scraping down sides to make sure everything is incorporated. Don't overmix!
Pour batter into prepared loaf pan and top with remaining grated cheese. Bake at 350 degrees F. in center of oven for 45 to 50 minutes or until toothpick inserted in several places comes out clean, and top is golden brown. (Insert the toothpick several times to avoid a false reading if you hit a "cheese pocket".)
Allow to cool 5 minutes on a wire rack. If loaf sticks to sides of pan use an offset spatula and run it around the edges of the pan to loosen. Allow the cheese bread to cool completely before cutting. It actually will cut better the next day!