01 - Cut cold butter into flour in a large bowl until mixture resembles coarse crumbs. Incorporate sourdough discard, sugar, and salt until soft dough forms. Shape into disk, wrap in plastic, and refrigerate for minimum 1 hour.
02 - Beat softened cream cheese in medium bowl until completely smooth. Blend in sugar, vanilla extract, and lemon juice until creamy and fully incorporated. Set aside at room temperature.
03 - Combine raspberries, sugar, cornstarch, and lemon juice in small saucepan. Cook over medium heat, stirring constantly, until mixture thickens noticeably, approximately 3-5 minutes. Remove from heat and allow to cool completely.
04 - Preheat oven to 375°F. Line baking sheet with parchment paper. Roll chilled dough on lightly floured surface to 1/4-inch thickness. Cut into 8 rectangles or circles, placing 2 inches apart on prepared baking sheet. Create indentation in center of each piece using fingers or spoon back. Fill each center with 1 tablespoon cream cheese mixture, topped with raspberry filling.
05 - Let assembled pastries rest at room temperature for 20-30 minutes until slightly puffed. Brush edges lightly with beaten egg. Bake for 20-25 minutes until golden brown and filling is set. Transfer to cooling rack.
06 - Whisk powdered sugar, milk, and vanilla extract until smooth consistency forms. Drizzle glaze generously over cooled pastries immediately before serving.