Why is my fried chicken batter soggy underneath? I dipped the chicken breasts in buttermilk, then a mixture of flour and potato starch, before frying at 390F for 3 mins. The chicken breasts were sous vide beforehand so the deep-frying step was just to give it the crust. 

However, I have noticed that the batter skin is always soggy underneath:
Are you allowing the buttermilk to drip off completely? I would either decrease the mixture (a scant coating), as it appears to be too much for this method of frying, or use a pre-made coating which is a bit thinner.