Mix the flour in a bowl with yeast, sugar, salt, milk, buttermilk, vanilla and baking soda. Mix to stick paste. Leave for 1 hour in a warm place or overnight in the fridge. Brew a shot of espresso. Heat deep frying oil (not in the list) to 180 degrees C. Flour a surface heavily, gather the dough into a ball, press it flat, and roll to 1/2 cm thickness. Cut into 5cm by 5cm square pieces. Stretch each carefully and lower into the heated oil. Fry each batch for about 80 seconds until golden brown. Remove and place on a kitchen towel in a bowl. In a separate bowl, pour the espresso into icing sugar. Whisk. Serve a stack of beignets dusted with the icing.