Preheat oven to 350°F (177°C). Line the bottom and sides of an 8-inch square baking pan with aluminum foil or parchment, leaving an overhang on all sides to easily lift the bars out of the pan before cutting. Set aside.

Using a food processor or blender, pulverize the graham crackers into a fine crumb. Pour into a medium bowl and mix with melted butter. Press into the lined pan. Bake for 8 minutes. Allow to cool as you prepare the filling.

Beat the softened cream cheese for 1 minute using a hand or stand mixer. Beat in the yogurt, egg whites, sugar, and flour until mixture is smooth and creamy, about 3 full minutes. Add the lemon juice and vanilla, beat for 1 additional minute until combined. Fold in the chocolate chips.

Remove the crust from the oven and spread filling on top. Bake for 25 minutes, covering the cheesecake bars at the 20 minute mark with aluminum foil to prevent browning. Allow to cool for 20 minutes at room temperature, then chill completely in the refrigerator for at least three hours. Lift the foil out of the pan and cut into squares.