Preheat the oven to 325°F (163°C). Line two baking sheets with parchment paper.
In a large bowl, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 3 minutes.
Add the vanilla extract and mix until combined.
In a separate bowl, whisk together the all-purpose flour and salt.
Gradually add the flour mixture to the butter mixture, mixing on low speed until the dough comes together and is smooth.
Roll the dough into a log about 2 inches in diameter. Wrap in plastic wrap and refrigerate for 30 minutes to firm up.
Remove the dough from the refrigerator and slice into 1/4-inch thick rounds. Place the rounds on the prepared baking sheets about 1 inch apart.
Bake for 20 to 25 minutes, or until the edges are lightly golden. Remove from oven and let cool completely on a wire rack.
Once cooled, spread about 1 teaspoon of raspberry jam on the bottom side of half of the cookies.
Top each jam-spread cookie with a plain cookie to form a sandwich. Press gently to adhere.
Serve immediately or store in an airtight container.