1. In a medium bowl, combine the cake mix, vegetable oil, and eggs. Fold in the white chocolate chips.
2. Preheat the oven to 350 degrees and line two cookie sheets with parchment paper.
3. Using a small cookie scoop (about 1-1/4″ diameter/1 tbsp of dough), add scoops of the dough to the cookie sheet, about 2″ apart.
4. Bake for 9-11 minutes or until set. Do not over bake because cookie sandwiches are much better with softer cookies!
5. Let them cool on the pan for 10-15 minutes then move to wire racks to cool completely.
6. To make the frosting, beat the butter until smooth. I use a standing mixer with paddle attachment, but you can also use a hand mixer. Add in half of the sugar and mix. Add in the rest of the sugar, heavy cream, and vanilla extract and mix. Gently fold in the preserves. You can mix it in all the way or leave it just lightly marbled throughout the frosting.
7. Spread the cookies out onto a flat surface.
8. Using a piping bag with an open tip, add a generous dollop of frosting onto half of the cookies. Be sure to flip each cookie before you add the frosting so that the top of the cookie is still showing. If you don’t have piping bags just use a knife and spread the frosting. Top with another cookie with the flatter part of the cookie touching the buttercream.
9. Repeat with the rest of the cookies and enjoy. Make sure to keep them refrigerated until serving since the raspberry makes the frosting a bit softer.