Preheat oven to 350° F. Line your 8 x 8 or 9 x 9 square pan with parchment paper and spray with cooking oil. Let it overhang on two opposite sides to make for easy removal.
Combine flour, cornmeal, sugar, baking powder, and salt in a bowl. Whisk together.
Add oil or butter, milk, and egg. Mix until combined.
Pour into an 8 x 8 or 9 x 9 square pan.
Bake 15-18 minutes or until a toothpick inserted into the center comes out clean. Remove from oven and cool for 10 minutes in pan, lift out entire piece square of cornbread using the overhanging pieces of parchment. Allow it to continue to cool all the way before cutting.
Cut cornbread into ½ inch cubes. Transfer to a bowl. Drizzle olive oil and sprinkle with salt if using it. Toss to coat.
Spread croutons out on a sheet pan. Bake in oven for 15-18 minutes at 350° F.