Whisk buttermilk, buffalo sauce, lemon juice, Dijon mustard, and 1 tbsp salt in a large bowl, or divide into more than one large plastic bag. Add drumsticks, making sure to cover them in the mixture.
Cover bowl with aluminum foil or plastic wrap, or zip the bag closed, removing as much air as possible. Refrigerate for at least 6 hours or overnight. Drain in a colander, shake off excess buttermilk, and reserve.
In a separate bowl, mix spices and 2 tbsp salt. Sprinkle on top of drumsticks, making sure to cover them all all over. In another bowl, whisk egg whites with water; reserve. In a baking dish, combine flour, cornstarch, baking powder, and 1/2 tbsp salt. Mix well.
Dip each drumstick in the egg mixture and then dredge in the flour mixture, making sure to cover them well. Shake off excess. Repeat process for all the remaining drumsticks.
Fill deep fryer with oil and heat to 350 F (or a dutch oven with a deep-fry/candy thermometer attached to the edge). Gently add the drumsticks, cooking in batches in order to not overcrowd the fryer.
Fry the chicken until cooked through and crispy (about 10 minutes), or until a probe thermometer inserted into the thickest part reads 165 F. Place fried chicken on paper towels to absorb oil. Serve while hot and enjoy by itself or with any sauce of your choice.
Store this extra crispy fried chicken in the fridge in a shallow airtight, or wrap tightly with heavy-duty aluminum foil/ plastic wrap for up to 4 days. Or, freeze in airtight containers or freezer bags for up to 4 months.