In a medium saucepan, bring the water to a boil. Add the rice and cook for 1-2 minutes.
Reduce the heat, add the milk, and simmer over low heat, stirring frequently, until the rice is tender and the mixture is thickened (about 30 minutes).
Stir in the salt and butter. Set aside to cool.
In a large bowl, mix the rye flour, all-purpose flour, and salt.
Gradually add the water, mixing until a smooth dough forms. Divide the dough into 12-15 small balls.
Preheat your oven to 425°F (220°C).
Roll out each dough ball on a floured surface into thin ovals or rectangles.
Spoon a portion of the rice filling onto the center of each dough piece, leaving a border around the edges.
Fold the edges of the dough over the filling, pinching to seal and create a slight fold along the length of the pastry.
Place the assembled pastries on a baking sheet lined with parchment paper.
Bake in the preheated oven for about 15-20 minutes, or until the pastries are golden brown.
In a small bowl, combine the chopped hard-boiled eggs with softened butter. Season with salt to taste.
Enjoy your meal!