01 -  Preheat oven to 400°F. Grease a 12-cup muffin tin or line with paper liners. 
 02 -  In a large bowl, whisk together all-purpose flour, baking powder, baking soda, and salt. 
 03 -  Add cubed cold unsalted butter to the flour mixture and cut in until the mixture forms coarse crumbs. 
 04 -  Stir in buttermilk just until a shaggy dough forms. Do not overmix. 
 05 -  Gently fold in cheddar cheese, mozzarella cheese, chives, minced garlic, chili flakes, and smoked paprika. 
 06 -  Divide dough into 12 equal portions and roll each into a ball. 
 07 -  Mix hot water and baking soda in a small bowl until baking soda dissolves. 
 08 -  Dip each dough ball briefly in the baking soda solution, then roll in crushed pretzels to coat evenly. 
 09 -  Arrange the coated balls in the greased muffin tin, one ball per cup. 
 10 -  Bake on the center rack for 16 to 18 minutes, until muffin balls are golden brown and puffed. 
 11 -  Brush the tops of the hot muffin balls with melted butter and finish with a sprinkle of flaky sea salt. Serve warm.