Best-Ever Chocolate Chip Sandwich Cookies

In a large bowl, beat melted butter and sugars with a mixer at medium speed until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add eggs and egg yolks, one at a time, beating well after each addition. Beat in vanilla.

In a medium bowl, whisk together flour, baking soda, baking powder, and salt. Reduce mixer speed to low. Gradually add flour mixture to butter mixture, beating just until combined. Beat in chocolate chunks and chocolate morsels. Cover and refrigerate for at least 2 hours or up to 3 days.

Preheat oven to 350°. Line baking sheets with parchment paper.

Using a ½-cup spring-loaded scoop, drop dough 2 inches apart onto prepared pans.

Bake just until edges of cookies are browned and tops are starting to brown, 12 to 15 minutes. Let cool on pans for 2 minutes. Remove from pans, and let cool completely on wire racks.

Spread desired amount of Buttercream onto flat side of half of cookies. Place remaining cookies, flat side down, on top of Buttercream. Store cookies in airtight containers for up to 5 days, or freeze in resealable plastic bags for up to 1 month.

In a large bowl, beat butter with a mixer at medium speed until creamy. Gradually add confectioners’ sugar, beating until combined. Add cream, beating until smooth.