In the bowl of a stand mixer fitted with a paddle attachment or in a large mixing bowl with an electric hand mixer, whip the room temperature unsalted butter for 5 minutes until light, pale, and creamy.
Add the Biscoff spread and mix until well combined and smooth.
Then, add in half of the powdered sugar and mix on the lowest speed until the sugar is combined with the butter.
Add the remaining half of the powdered sugar and continue to mix on low speed until fully combined.
Add the vanilla extract and salt.
While mixing on low speed, drizzle in the heavy cream.
Scrape the sides and bottom of the bowl to ensure the ingredients are well incorporated.
Increase the mixer speed to medium and whip the buttercream for about 2 to 3 minutes until it is smooth and creamy.
To smooth out the buttercream and remove any air bubbles, mix the frosting on low speed for several minutes.
