In The Way Back (2010), there is one scene where Mr Smith is shown eating dirt from under his boot.
It is continuous shot, no cuts.
You take two cups of flour, 2 eggs and some chocolate milk. You mix the two cups of flour in a bowl together with the eggs. When it's getting a mud like form, you mix in the chocolate milk until you reach the desired dirt color. You can add some sugar, depending on taste.
Cover the paste up and put it in the refrigerator until needed.
Apply to boot with a spatula and preferably walk on a clean floor before ingesting.