Microwave the butter, in a small bowl, at 30% power for 20-40 seconds. The butter could bubbly over, so watch closely the last 10 seconds. Add the oil to the melted butter and stir well.
Add the salts, black pepper, your favorite herbs/seasonings to the butter/oil mixture and add the bread cubes. Toss until cubes are evenly coated in the oil/butter mixture.
Pour the croutons onto a foil-lined rimmed baking sheet and bake 15-25 minutes, stirring and flipping after 8 minutes. Bake until golden brown and crisp.
Sprinkle with the grated Parmesan cheese and toss until all croutons are covered.
Allow to cool completely.
The croutons will keep in an airtight container up to 3 weeks, but I promise you they won't last that long.
Original recipe: J.Kenji Lopez-Alt: The Best Caesar Salad Recipe