In the bowl of an electric mixer fitted with the paddle attachment, beat butter and sugars until creamy, 1-2 minutes. Beat in eggs and vanilla extract, scraping the side of the bowl to make sure everything is incorporated. Add flour, baking soda, and salt and mix until smooth. Use a wooden spoon or rubber spatula to stir in the chocolate chips. Cover the bowl and refrigerate the dough 1 hour to overnight.
Preheat the oven to 350ºF. Roll chilled dough into smooth, 1 inch balls. Flatten balls into ¾ inch disks. Place disks about 2 inches apart on a parchment or Silpat lined baking sheet. Bake 9-11 minutes until cookie edges are slightly golden brown. Let cool for 5 minutes on the baking sheet. Transfer to a wire rack to cool completely.
To make the cookie dough, beat together butter and brown sugar in a large bowl with an electric mixer on medium speed until light and fluffy, about 2-3 minutes. Mix in flour, powdered sugar, and salt on low speed until incorporated. Slowly add heavy cream and vanilla extract and beat until fluffy, about 2 minutes. Stir in mini chocolate chips.
To assemble, spread 1 heaping tablespoon or more of filling onto one cookie and top with another. Press the cookies together gently to stick together. Repeat with remaining cookies.
Sandwiches can be stored in an airtight container in the refrigerator for up to 3 days. Let sit at room temperature for 30 minutes before serving.