Gather all ingredients.

Beat together milk and eggs in a large bowl until combined.

Beat in sugar and salt. Mix in baking soda and citric acid until incorporated.

Blend in flour, a little at a time, until combined. Beat in oil. Pour in boiling water, stirring constantly, until batter is thin and watery. Let rest for about 20 minutes.

Brush a small frying pan with 1 tablespoon melted butter over medium-high heat. Pick the pan up off the heat. Pour in a ladleful of batter while you rotate your wrist, tilting the pan, so batter forms a circle and coats the bottom. The blini should be very thin.

Return the pan to the heat. Cook blini for 90 seconds. Carefully lift up edge of blini to see if it's fully cooked: edges will be golden and bottom surface should have brown spots.

Flip blini over and cook for 1 minute more.

Transfer blini to a plate lined with a clean kitchen towel.

Continue cooking remaining batter, adding 1 tablespoon butter to the pan for every 4 blinis. Stack blinis and cover with another kitchen towel to keep warm.

Spread desired filling in the center of each blini.

Fold 3 times to make a triangle shape or fold up all 4 sides, like a small burrito.