For the cupcakes: Preheat the oven to 325 degrees F. Line standard cupcake pans with 36 standard cupcake liners.
Sift the flour, baking powder, and salt into a medium bowl. Set the bowl aside. In the bowl of an electric stand mixer, cream the sugar and margarine with the whisk attachment, about 5 minutes. Scrape down the sides and bottom of the bowl. In a small bowl or cup, combine the water and egg replacer and stir to dissolve the egg replacer. Add the egg replacer to the sugar and mix until combined. Scrape the bottom of the bowl. Add the ginger juice and mix until combined. In a small bowl, combine the soy milk and vanilla and set aside. Turn the mixer speed to low and slowly add the dry ingredients and the soy milk, alternating between the 2, ending with the soy milk. Fold in the minced ginger by hand into the batter.
Fill the cupcake liners 3/4 full with batter and bake until a toothpick inserted into each cupcake comes out clean, 19 minutes. Cool the cupcakes completely.
For the filling: In a medium, heavy-bottomed saucepan, stir together the puree and sugar. Heat on medium-high heat until the mixture begins to bubble around the edges. In a small bowl, mix the water or brandy and cornstarch into a slurry. Slowly add the cornstarch mixture to the puree while whisking. Cook for 2 more minutes while stirring. Let cool completely. Put the cooled peach filling into a piping bag and cut 1/2 inch off the tip.
For the frosting: In the bowl of a stand mixer, whip the shortening and margarine until completely combined. Scrape the bottom of the bowl to ensure that all the ingredients are mixed thoroughly. Add the blueberry puree and vanilla and mix until incorporated. Scrape the bottom of the bowl. On low speed, slowly add the sugar a little at a time. Add the blueberry juice and mix to combine. Scrape the bottom of the bowl and mix on medium-high speed until all the ingredients are combined and the frosting is fluffy, about 2 minutes. Put the frosting into a pastry bag and cut 1/2 inch off the tip.
To assemble: With a plastic drinking straw or a small paring knife, make holes in the center of each cupcake. Squeeze the peach filling into the center of each cupcake until filled but not overflowing, about 1 tablespoon per cupcake. Pipe a dollop of blueberry frosting onto each cupcake. Garnish with a few fresh blueberries, if using.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.