When the Lofthouse frosted cookies were first produced from a handed-down family recipe in a makeshift bakery in the back of a Utah garage in 1994, it's likely the ingredients were different than they are in the mass-produced product found in markets across the country today. To maintain a long shelf-life, it is common for baked goods to be manufactured with nondairy substitutes, so butter is often replaced with hydrogenated oil and butter flavoring (otherwise known as margarine), and various vegetable gums and preservatives are added to improve the texture and stabilize the product.
Rather than using ingredients such as artificial flavoring, lecithin, cellulose gum, or carrageenan in my Lofthouse cookie recipe, as you will see on the label of the store product, we will use real butter, fresh eggs, and vanilla extract in our clone - perhaps just as the family who created this recipe did back in the day. The big difference is that you have to be sure to eat the cookies within a few days to get that freshly baked taste and texture. Or you may want to freeze them. Cake flour is used here rather than all-purpose flour to duplicate the tender, cakey texture of the original, and sour cream is used to add in the dairy needed without overliquefying the dough (as milk would). An added benefit of sour cream is the high acidity, which activates the leavening power of the baking soda. The dough is still going to be much thinner and tackier that typical cookie dough, so chilling it for a couple of hours before portioning it out onto a baking sheet is a must to make it easier to shape.
Get the full recipe in Todd Wilbur's "Top Secret Recipes Step-by-Step" cookbook.