Line a not too large, rectangular container with baking paper.
Roast sunflower seeds in a coated pan without fat over medium heat, stirring, until golden, about 10 - 15 minutes.
Immediately transfer the roasted sunflower seeds to a clean bowl and let cool.
Using a high-powered blender, puree the sunflower seeds to a spreadable mass (sunflower seed paste) and transfer to a mixing bowl.
Add sugar and water to a saucepan and bring to a boil over medium heat, stirring so that the sugar dissolves before the syrup boils.
Let the sugar syrup boil over medium heat, without stirring it, until it reaches 248 °F - 252 °F (120 °C - 122 °C). For me, it took about 5 minutes.
Beat egg white with salt in parallel to make beaten egg white.
Start beating the egg white again and immediately pour the hot sugar syrup in a thin stream.
After you have introduced the sugar syrup into the beaten egg white, beat the egg white mixture for another 1 - 2 minutes so that it becomes glossy and chewy.
Immediately add the egg white mixture to the sunflower seed paste and mix.
Put the halva mixture into the container lined with baking paper, press it down, cover it with baking paper and refrigerate it for about 2 hours.
Take the halva out of the container and cut it into pieces.