Don't skip the first step: For the fluffiest, puffiest puddings, make sure the muffin pan is super hot. You can also make these in popover pans.
Preheat oven to 450°. Heat a 12-cup muffin pan in oven 15 minutes.
Meanwhile, cook bacon in a medium skillet over medium heat, stirring occasionally, 8 to 9 minutes or until crisp. Remove bacon, using a slotted spoon, and drain on paper towels. Reserve drippings.
Whisk together flour and kosher salt in a large bowl. Whisk together eggs and milk in a medium bowl. Gently whisk egg mixture into flour mixture until well blended. Stir cheese, chives, and cooked bacon into flour-egg mixture.
Spoon 1 tsp. bacon drippings into each cup of hot muffin pan; place muffin pan in oven for 2 minutes. Carefully remove pan. Divide batter evenly among cups.
Bake at 450° for 25 minutes or until puffed and golden brown. (Center will still be wet.) Serve immediately.
I made these during the holidays, and they are delicious with prime rib and creamed corn!