Preheat oven at 350F. Grease a 7-inch spring form pan.
Make the crust by mixing all the crust ingredients together in a food processor or with a fork.
Press the mixture onto the bottom of the spring form pan. Bake crust for 5 minutes. Set aside to cool. Turn down oven temperature to 250F.
To prepare filling, beat the cream cheese and peanut butter on medium speed until smooth in a standing mixer fitted with a paddle attachment. Add brown sugar and beat to combine. Then add egg, heavy cream and vanilla extract, mix for 2 minutes or until well blended.
Pour the filling over the cooled crust. Tap the pan on counter a few times to release all the air in the batter. Bake for 45 to 50 minutes, or until the edge of the cheesecake is puffed but the center is still wobbly and wet looking.
Turn off the oven with the door slightly opened, let the cheesecake sit in the oven to cool completely, at least an hour.
Chill for at least 4 hours, or preferably overnight.
Before serving, leave the cake in room temperature for 30 minutes.
To prepare frosting, in a large heatproof bowl, combine sugar and egg whites. Using a handheld electric mixer, beat on high speed until foamy for a minute. Set bowl over a pan of barely simmering water. Beat on high speed until frosting form stiff peaks, about 10 minutes.
Remove from heat, stir in vanilla and water, and beat for another 2 minutes until frosting thickens.
Smear the meringue frosting thickly on the top of the cake. Using a small metal spatula to create swoops and peaks.