Preheat oven to 350 degrees F.
Line an 8 by 8-inch baking pan with parchment paper. Lightly grease and flour.
In a standing mixer with the paddle attachment, cream together, butter, sugar, vanilla seeds and vanilla extract. Add eggs and mix until well incorporated.
Mix together the dry ingredients and slowly add it to the egg mixture. Mix until well incorporated.
Pour the batter into prepared pan and spread evenly, add hazelnuts to the top.
Bake for 22 to 25 minutes until brownies are set and begin to pull away from the side.
Remove from oven and let cool on wire rack. Once cooled, remove brownies from pan and cut into 1 1/2-inch squares for individual bites.
For the frosting:
In a large bowl, use an electric mixer to cream butter and slowly add the powdered sugar. Add grenadine and mix until a frosting consistency is reached.
Place frosting in a piping bag and pipe onto individual brownie bites.