Preheat the oven to 350 degrees F. Line cupcake pans with 24 liners.
In a medium bowl, combine both flours. Using an electric mixer with the paddle attachment, cream the butter until smooth. Gradually add the granulated sugar and beat until fluffy. Add the eggs, one at a time, beating well after each addition. Add the flour mixture in three parts, alternating with the milk. Add the vanilla. Scrape down the sides of the bowl to make sure all the ingredients are well blended. Beat until just combined. Do not over beat. Fold in the caraway seeds.
Spoon the batter into the liners, filling the cups two-thirds full. Bake until a toothpick inserted in the center comes out clean, about 16 minutes. Cool the cupcakes completely.
Cut the tops off the cupcakes and reserve. Place the chopped pastrami on the bottom half of the cupcakes. Drizzle 1 teaspoon Honey Mustard Glaze (more or less to taste) on the pastrami. Place the cupcake tops on top of the glaze, pressing down gently. Frost the cupcakes with Honey Mustard Buttercream Frosting. Garnish with soft pretzel slivers.
In a small bowl, combine the powdered sugar, honey and mustard, and mix until smooth.
Using an electric mixer with the paddle attachment, cream the butter until smooth. Add the honey mustard and spicy mustard and mix on high for 1 minute, scraping down the sides often. Add the powdered sugar 1/4 cup at a time, mixing well after each addition.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.