Remove the stems from the greens, place them in a large bowl with water. Let them sit for 5 minutes. All the sand/dirt will fall to the bottom. Remove the greens, dump the water, and repeat until your greens have been washed thoroughly and no longer have dirt/sand on them.
In a large sautéed pan (fitted with a lid) place the olive oil, butter, and garlic in the pan and cook for 1 minute (or until butter is melted) on high heat. Reduce the heat to medium and begin to add the greens. Place all the greens in the pan, put the lid on the pan and cook for 10 minutes. Greens should begin to wilt. Carefully stir, the greens (moving the top greens to the bottom and the bottom greens to the top). Cook an additional 5 minutes longer then serve.
Take the time to properly wash your greens to avoid a gritty side dish.
Roast your beets and save the greens for a vitamin packed side dish. Absolutely no waste when you get to use the beet greens, too.