Grease the inside of a microwave-safe mug (both interior sides and bottom). Add graham cracker crumbs and melted butter and mix until butter is completely mixed into the crumbs. Press down on the crumbs with your fingers to form a crust at bottom of mug. You want the crumbs to be tightly pressed together, so make sure to apply some pressure.

In a medium bowl, add egg, cream cheese, yogurt, sugar and vanilla. Using a small whisk, mix until batter is smooth. There may still be tiny lumps of cream cheese left depending on if you used regular cream cheese or cream cheese spread, but you want to get them as small as possible. Pour batter into mug.

Cover top of mug with a paper towel and microwave for 1 minute at full power. Mug cake should be mostly cooked except center. Pause to check on it, then microwave for another 20 seconds. Stop again, and microwave for another 20 seconds. Then microwave for one final round of 20 seconds. Cake should be completely cooked. You don't want to microwave the entire amount at once because the batter may overheat and splatter.

If you have greased your mug, the cheesecake should have pulled away from the sides of the mug. Gently slide cheesecake out of the mug. I let it come out upside down onto a big spatula and then flipped it back over onto a plate. Let cool cake at room temperature for a few minutes. Place in fridge to cool and set for at least 1 hour. Please let cheesecake cool and set before eating. It will not taste like cheesecake if you try to eat it right away.