To make brown butter buttercream filling:
1. In a medium pot or skillet, cook butter over medium heat. Stirring occasionally, cook about 10 minutes until butter reaches a golden brown. Remove from heat and allow to cool to room temperature. The butter will be somewhat solidified, but not hard (you can speed up this process by placing butter in refrigerator.)

2. Once cooled, use a stand mixer to beat butter until light and fluffy. Add heavy cream, vanilla extract and powdered sugar.

3. Slowly mix ingredients together until almost combined. Continue to beat mixture on high for 5-7 minutes until light and fluffy.

4. Place buttercream into a piping bag with a piping tip of your choice.

To make cookies:
1. Preheat oven to 350°. In a medium pot or skillet, gently melt butter over low heat.

2. Meanwhile, in a large bowl, whisk together flour, baking powder, baking soda, salt, lemon zest and ground cardamom. Set aside.

3. Add sugar to a mixing bowl of a stand mixer. Once butter is melted, but not hot, add to sugar. Mix using paddle attachment. Add vanilla, egg and yolk to the bowl. Mix until combined.

4. Add dry ingredients and mix until fully combined. Using a 3-ounce cookie scoop, scoop the cookie dough onto a parchment lined sheet pan. You will get approximately 13 cookies (one extra cookie to taste test, of course!) Bake cookies for about 14-16 minutes. Allow cookies to cool completely before assembling sandwiches.

To assemble:
1. Pipe a thick swirl of buttercream on 12 cookies. Top each with another cookie.

2. Drizzle one half of the sandwich cookie with melted white chocolate. Before the white chocolate sets, top with candied lemon peel.