Step 1: In a medium bowl, combine the graham cracker crumbs, melted butter, and 1/4 cup granulated sugar. Mix thoroughly until the crumbs are evenly moistened.
Step 2: Press the mixture firmly into the bottom of an 8x8 or 9x9 inch greased baking dish, forming an even crust. Place in the refrigerator to chill for at least 30 minutes.
Step 3: While the crust chills, prepare the rhubarb filling. In a saucepan, combine the chopped rhubarb, 1 cup granulated sugar, water, lemon juice, and vanilla extract.
Step 4: Cook over medium heat, stirring occasionally, until the rhubarb is very soft and the mixture has thickened, approximately 10-15 minutes.
Step 5: Remove the rhubarb filling from heat and let it cool completely to room temperature. This is crucial for the dessert's consistency.
Step 6: Once cooled, spread the rhubarb filling evenly over the chilled graham cracker crust in the baking dish.
Step 7: Return the dessert to the refrigerator and chill for a minimum of 2 hours, or until it is completely set.
Step 8: Before serving, garnish with whipped cream and chopped nuts. If desired, add fresh rhubarb stalks and mint leaves for an elegant touch. Serve immediately and enjoy your delicious no-bake treat!