Double Digging my raised beds with compost.

I have started preparing my raised beds for next spring. I might yet try to plant some mustard greens. This is where my corn was grown. I found out that in about three hours I can double dig a twenty by 3 foot raised bed. I dig a trench and then fill it  pretty much to the top with compost. Then you move over about twelve inches and dig a new trench and throw the dirt on top of the compost. So the whole bed is sort of floating on twelve inches of compost. At the bottom of the trench, before you add the compost, you take a potato fork and push it all the way. Then rock it back and forth to break up the subsoil. I also had to use a mattock/hoe. The subsoil is almost pure clay, and hasn't been broken up in several thousand years. The French Market gardeners who invented the intensive gardening system used to use horse manure and bedding. They would fill the trench and tromp it down every time they would work there beds. The horse manure heats up, providing bottom heat, and allowing the gardener to start his garden earlier in the spring and continue into early winter. They also used wooden frame sides and windows on top to have miniature green houses. This way in their intensive French gardening system they could have high plant populations and maximum production . In the 17 and 1800's near Paris they had a highly developed production system.