In a stand mixer with a paddle attachment, beat the softened butter and confectioners' sugar on medium speed for exactly 2 minutes until pale and creamy.

Mix in the vanilla extract and kosher salt. Turn the mixer to low speed and gradually add the all-purpose flour until the dough just begins to clump together. Do not overmix.

Turn the dough out, gently knead it into a ball, and divide it in half. Flatten into two 1-inch thick disks, wrap tightly in plastic wrap, and refrigerate for at least 1 hour.

Preheat oven to 350°F (175°C). Roll the chilled dough on a floured surface to 1/4-inch thickness. Use a heart-shaped cutter to stamp out cookies and place them on parchment-lined baking sheets.

Bake for 10 to 12 minutes until the edges are golden-baked. Let cool on the pan for 5 minutes, then transfer to a wire rack to cool completely.

Blend half the freeze-dried strawberries into a powder. Whisk the powder with sifted confectioners' sugar and milk until a smooth, light pink icing forms.

Dip half the cooled cookies into the pink icing and immediately sprinkle with the remaining crushed freeze-dried strawberry flecks. Let set completely. Spoon 1 tsp of thick strawberry jam onto the bottom cookies, then top with the set, iced cookies.