Preheat the oven to 350 degrees Fahrenheit. Prepare your baking sheet by lining it with parchment paper or a silicone baking mat. Put it aside.
Combine the margarine, butter, and sugar in a stand mixer or with an electric hand mixer until well combined.
Using a spatula, scrape down the sides of your bowl before adding the egg, corn syrup, butter, and vanilla extract.
Combine the baking soda, flour, and salt to make a dough. Divide the dough into portions of 2 1/2 tablespoons. Place the dough ball on a baking sheet. Keep repeating the process until all the dough has been used up.
Bake in the preheated oven at 350°F for about 12 to 14 minutes. As soon as the cookie is taken out of the oven, it flattens and spreads.
Cool the cookies in the pan for five minutes before transferring them to a wire cooling rack. You can store it in an airtight container at room temperature for three days or in the freezer for two months. Enjoy!