In a small saucepan, melt the butter over medium heat and cook until it turns light golden and fragrant. Remove from heat and let it cool slightly.
In another bowl, whisk together the egg yolk, sugar, and vanilla extract until smooth.
Add all-purpose flour, baking powder, and salt to the same bowl and mix until a soft dough forms.
, Take small portions of dough and press them into a spoon to form oval shapes. Gently release onto a lined baking tray.
Bake in a preheated oven at 180°C for 10–12 minutes, or until the cookies are lightly golden.
Once the cookies have cooled down, spread a small amount of berry jam on the flat side of one cookie and sandwich it with another. Dust lightly with icing sugar before serving.
Recipe by Bake with Shivesh at https://bakewithshivesh.com/lusikkaleivat-finnish-cookies/