To make the rose shortbread cookies:

• In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and powdered sugar on medium speed for 90 seconds, until combined and creamy. Scrape down the sides of the bowl. Add in the rose water, vanilla extract, and kosher salt, and mix until combined.
• Combine the flour and cornstarch together in a separate bowl, then sift these ingredients together directly into the butter mixture. Turn the mixer on low speed and mix until the ingredients just come together and the dough is no longer crumbly. Be careful not to overmix.
• Shape the cookie dough into a disc and wrap tightly in plastic wrap (TIP: if the dough is a little sticky, you can lightly flour your hands to make shaping the dough easier). Place the dough in the fridge to chill for 30 minutes. In the meantime, preheat the oven to 325°F and line two baking sheets with parchment paper.
• Place the chilled dough on a well-floured surface. Lightly flour the top of the dough and your rolling pin to prevent sticking. Roll the dough out until it’s 1/4″ thick, lightly dusting the dough and rolling pin with more flour as needed.
• Using a 2″ cookie or biscuit cutter, cut the dough into rounds. Place the cutouts on the prepared baking sheets, spacing about 1″ apart. Re-roll out the scraps of dough and continue this process until you’ve used up all the dough (TIP: if the dough starts to get too soft, pop it back in the fridge for a few minutes to firm up).
• Sprinkle the cutouts with granulated sugar and place in the freezer for 10 minutes.
• Bake for 15-18 minutes, rotating the baking sheets from front to back halfway through. The cookies are done when the tops appear dry and matte. Allow the cookies to cool on the baking sheet for 10 minutes before removing to a wire rack to cool completely.

To make the strawberry buttercream filling:

• Place the pureed strawberries and 2 tablespoons of water in a small saucepan over medium-low heat. Cook, stirring constantly, until reduced and thickened, about 6-8 minutes. Strain the mixture through a fine mesh sieve into a heatproof bowl. Set aside to cool.
• In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and cream cheese together on medium speed until combined and creamy, about 1 minute. Add in the lemon zest and kosher salt and mix to combine.
• Add in the powdered sugar, heavy cream, and 45 gm (3 tablespoons) of the cooled strawberry puree. Turn the mixer on low to allow the ingredients to come together, then gradually increase the mixer to medium-high speed, beating until the buttercream is light and fluffy, about 1 minute. Reduce the mixer speed to low and beat for another 30 seconds until smooth. Use immediately.

Assembly:

• Transfer the strawberry buttercream to a piping bag fitted with a star piping tip (I used an Ateco #21 tip). Pipe a swirl of buttercream onto the underside of one cookie. Place another cookie on top and gently press to adhere, forming a sandwich. Repeat this process until you have used up all the cookies!