Prepare a pastry bag (or a regular thick plastic bag) and a sheet of baking paper on a board in advance.

You can take any fruits or berries you like (we tested strawberries, blueberries, and cherries). You can also take frozen ones; they just need to be defrosted. Puree the fruits or berries with a blender, and if there are large seeds left (for example, if you have blackberries or currants), rub the puree through a sieve. While you are making the puree, pour cold water over the agar and let it stand.

As soon as the puree is ready, add half the sugar and agar with the water and mix well. Let it stand until the sugar is completely dissolved.

Beat the whites with a pinch of citric acid and gradually add the second half of the sugar until they form medium peaks. Then, put the fruit puree with sugar and agar on high heat until boiling, stirring well in the process so that the agar does not collect on the bottom. When the puree starts to actively boil, reduce the heat and cook for precisely 3 minutes. Check the temperature if you have a cooking thermometer - it should be 93 C. If you don't have a thermometer, watch the bubbles - by the end of cooking, they are already quite large and burst a little more slowly.

When the syrup is ready, continue whipping the whites and adding the syrup in a thin stream. Beat until fluffy and airy at the highest speed. The mass should increase in volume, lighten, and thicken. It should be dense and wrap around the mixer's whisk.

Transfer the mass to a pastry bag and pipe marshmallows in the shape you like. Let them stabilize and stand overnight in a cool place.

You can eat it as is, or sprinkle it with powdered sugar and starch.