Preheat your oven to 350°F (175°C). Grease or line an 8x8 square baking pan with parchment paper.
Cream the butter: Using a stand mixer: Fit your mixer with the paddle attachment and beat the butter on medium speed until smooth and creamy, about 2-3 minutes. Using a hand mixer: In a large bowl, beat the butter on medium speed for 2-3 minutes until it’s light and fluffy. Mix dry ingredients: In a separate bowl, whisk together flour, cornstarch, salt, pepper, and garlic powder. Gradually add to the butter and mix on low speed until a dough forms.
Incorporate herbs and cheese: Stir in the rosemary, thyme, parsley, Parmesan, and lemon zest.
Press into pan: Spread the dough evenly in the prepared pan. Smooth the surface and lightly score into batons. Prick with a fork for decoration, if desired.
Bake: Bake for 25-30 minutes, or until the edges are golden.
Cool and cut: Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Cut into batons and serve.
Store these shortbread batons in an airtight container at room temperature for up to a week. For longer storage, freeze them in a single layer, then transfer to a freezer-safe bag or container for up to 2 months. To enjoy them warm, reheat in a 300°F (150°C) oven for 5-7 minutes.