In a medium saucepan, combine rhubarb, 1/3 cup sugar and orange juice. Bring just to boiling; reduce heat. Cook, uncovered, about 5 minutes or until rhubarb is tender, stirring occasionally; set aside.
In a heavy small saucepan, melt white chocolate baking squares over very low heat, stirring occasionally. Set aside to cool.
In a medium bowl, combine graham crackers and butter. Press crumb mixture onto the bottom and about 1-1/2 inches up the sides of a 10-inch springform pan. Wrap outside of the springform pan securely with heavy foil. Set aside.
In a very large bowl, beat cream cheese, sour cream, 1/2 cup sugar, cornstarch, vanilla and salt with electric mixer on medium speed until well blended. Add eggs, 1 at a time, beating just until combined after each addition. Gradually beat in melted white chocolate until combined.
Pour half of the filling into crust-lined pan. Spoon 1 cup of the rhubarb sauce over the filling, spreading evenly. Top with remaining filling. Spoon remaining rhubarb sauce over filling. Using the back of a spoon, gently swirl the rhubarb mixture into the filling.
Place springform pan in a large roasting pan. (Make sure there is at least 1 inch between springform pan and edges of roasting pan.) Place roasting pan on oven rack. Carefully pour enough boiling water into roasting pan to come halfway up sides of springform pan.
Bake in a 350 degree F oven for 1-1/2 to 2 hours or until edge of cheesecake is firm and center appears nearly set when lightly shaken. Check water level every 30 minutes, adding more water if needed. Carefully remove cheesecake pan from water bath; transfer to a wire rack and cool for 15 minutes. Remove foil. Loosen cheesecake from sides of pan by carefully running a knife around the edge of the pan. Cool cheesecake for 30 minutes more. Remove sides of pan and cool completely. Cover cheesecake with plastic wrap and chill at least 4 hours before serving.
If you like, just before serving, pipe rosettes of whipped cream on the top of the cheesecake and garnish with white baking bar curls and mint. Cut into wedges. Makes 12 to 14 servings.
Prepare, bake, and thoroughly cool the cheesecake. Cover tightly with plastic wrap. Store in the refrigerator for up to 2 days ahead.