In a medium bowl, stir together the graham cracker crumbs, butter and sugar; pat into the bottom of a 9-inch springform pan, and up 2-inches on the sides of the pan too. Place the pan in the freezer while you prepare the cheesecake filling.
PREPARE THE CHEESECAKE:
Preheat the oven to 350 degrees F. Place a pan of water on a lower rack of the oven (this will help prevent the cheesecake from cracking while baking). Place the second rack in the middle of the oven.
In a large bowl, use a hand mixer to combine the cream cheese, yogurt and sugar. Beat until fluffy; add eggs, one at a time, beating well after each addition. Beat in the vanilla. Scrape the cheesecake batter into the frozen crust.
Place the cheesecake on the middle rack above the pan of water, and bake for 50 minutes. THEN TURN OFF THE OVEN AND LET THE CHEESECAKE STAY IN THE OVEN (you can turn on the light to take a peek, but don't open the oven) FOR 90 ADDITIONAL MINUTES.
PREPARE THE TOPPING:
In a medium bowl, use a whisk to combine the sour cream, sugar and vanilla.
After the 90 minutes, remove the cheesecake from the oven and add the sour cream topping. Spread it evenly on top of the cheesecake. Refrigerate overnight.
SERVE:
Remove the springform ring (use a sharp knife down the sides if you think the cheesecake has stuck to the pan). Garnish cut slices with fresh berries.