In a mug or small bowl, stir together melted vegan butter, brown and white sugar, vanilla extract, baking soda, yogurt (or milk), and a pinch of salt.
Add in flour and stir until just barely combined. (Be sure to measure flour properly. Don't pack it down into the measuring cup or you'll have dense cookies.) Then stir in the chocolate chips.
Pop the bowl of cookie dough in the fridge, then set your oven to preheat to 350°F. Let the dough chill for however long it takes for your oven to preheat, or for at least 10 minutes.
Once the dough has chilled and your oven has preheated, divide the cookie dough into portions and roll into balls. Place them on a cookie sheet. (I recommend lining with parchment or a silicone baking mat if you have one, though it's not strictly necessary.) There's no need to press the cookies down; they'll spread on their own in the oven.
Bake the cookies for 11-14 minutes, depending on your preference.Soft and gooey cookies: Try 11 minutes. The cookie should be set and a bit browned around the edges but still appear undercooked in the center.Well-done cookies: try 14 minutes, or until the cookie is evenly browned and appears fully set in the center. Allow the cookies to cool for at least 5 minutes on the tray before enjoying.