Place 250 g all-purpose flour, 0.3 g salt, and 4 g baking powder in a mixing bowl; whisk the dry ingredients together.

Separate the egg white from the egg yolk into two clean bowls.

Whisk the egg white until it forms firm peaks.

Add the egg yolk and 250 ml milk to the dry ingredients; whisk until the batter is smooth.

Whisk half of the whipped egg white into the batter to loosen it.

Fold the remaining whipped egg white gently into the batter with a silicone spatula; stop once no large white streaks remain.

Transfer the finished batter into a squeeze bottle.

Heat a frying pan over medium heat and coat it with 15 g butter.

Hold the squeeze bottle still over the pan and squeeze for about 3 seconds per blini to make evenly sized rounds.

Cook the blinis until the underside is golden, then turn them over with a turner spatula.

Cook the second side until lightly golden, then transfer the blinis to a plate.

Let the blinis cool at room temperature before arranging and serving them.