To make buttermilk for this recipe, take ¾ cup milk in a cup, and take 2 tsp milk out of it and add 2 tsp of vinegar in it, stir to mix. Leave it for 2 to 3 min, it;ll thicken up. That's buttermilk for this recipe.
I melted butter in microwave in 10 sec sessions. Stir and then leave it for another 10 sec in microwave. If little unmelted chunks/lumps left, leave it outside for 2 to 3 minutes after microwaving, it'll melt on its own in hot buttery liquid.
Leave a recognizable mark around the side of the bowl or some indication on the bowl to show the height of your dough at this stage one, so when the dough doubles in size you know how big it had gone, ok?
Lukewarm water is 2 parts hot water, 1 part regular room temperature water.
Frying: Heat oil till a tiny bit of the dough starts sizzling as soon as you dip it into it. And then monitor and adjust if the donuts are getting too dark too quickly. Fry in medium hot flame.