1. Halve rhubarb stalks lengthwise, then cut into 2 1/2"-long pieces. In a medium bowl, toss rhubarb with 3 tablespoons confectioners' sugar, then let sit until softened, about 30 minutes, tossing occasionally.
2. Meanwhile, on a lightly floured surface, trim pastry into a 9" square, then cut into nine 3" squares. Working with one square at a time, gently press a 2"-wide round cookie cutter into center, being careful not to punch all the way through. Pierce inside of circle all over with a fork, then transfer to a parchment-lined baking sheet and refrigerate until ready to use.
3. Center a rack in oven and heat to 400 degrees. In a small bowl, mix cream cheese, 1/4 cup sugar, and the vanilla. Brush egg over edges of pastry, leaving each circle bare, then spread about 1 tablespoon cream cheese mixture inside each circle. Arrange rhubarb pieces over cream cheese mixture, reserving juices left in bowl.
4. Bake until rhubarb is tender and pastry is puffed and golden brown, about 20 minutes, rotating baking sheet halfway through. Transfer danishes to a wire rack and let cool 10 minutes.
5. Meanwhile, mix remaining 1/4 cup sugar with 2 teaspoons reserved juices until smooth, adding more liquid 1 teaspoon at a time if glaze is very thick. Drizzle evenly over danishes and sprinkle with pistachios. Serve warm or at room temperature.
Source: Hannaford fresh Magazine, May-June 2021