I don't spend much time trying to re-create treats from the grocery store cookie aisle, partly because I've never tried the vast majority of them, and mostly because what I have tried has been entirely forgettable. (Equal parts "I couldn't remember that if I tried" and "Please don't make me".)
Then there are Oreos, which I love. I don't completely understand the attraction myself, but suspect it has something to do with the sharp contrast of the super sweet filling and intensely chocolate—almost salty—biscuit. There is also, of course, a certain joy that comes with splitting the halves and nibbling one wafer plain, all in the name of a better icing-to-cookie ratio in round two. These ratios, they're a recurring theme with me.
1 1/4 cups all-purpose flour
1/2 cup unsweetened cocoa
1 teaspoon baking soda
1/4 teaspoon baking powder
1/4 teaspoon salt
1 1/4 cup sugar
1/2 cup plus 2 tablespoons unsalted butter, at room temperature
1/4 cup unsalted butter, at room temperature
1/4 cup vegetable shortening
2 cups icing sugar, sifted
2 teaspoons vanilla extract
Notes: I was amazed how much these tasted like the real deal. Texture-wise, they're crunchy but have a pleasing give that's absent from the store-bought variety.
Source: Recipe from My Baking Addiction, who got it from Smitten Kitchen, who got it from Wayne Brachman's Retro Desserts.