[header] How to make homemade blueberry poptarts [title] Combine 2 1/2 cups flour , 3 tablespoons sugar and 1 teaspoon salt in a large bowl. [title] Slowly shred 1 cup cold butter using crosswise motion on a grater. [title] Place shredded butter into the bowl together with the dry ingredients. 
[step] Mix until thoroughly combined using your fingers. [title] In a small bowl, beat the egg yolk with water, reserving the egg white until later.