Position rack in lower third of oven and preheat the oven to 425ºF.
Sift the flour, mustard, and salt into a medium mixing bowl and add the Essence or other Creole seasoning.
Make a well in the center of the flour mixture and add the egg and
1/4 cup of the milk. Using a whisk, mix the egg and milk into the flour mixture a little at a time, adding the remaining cup of milk little by little to form a smooth batter. Do not overmix. Set the batter aside to rest for at least 30 minutes.
Grease the wells of a nonstick muffin tin with 1/2 teaspoon each of the bacon drippings or vegetable oil. Divide the sausage and onion evenly among the wells. Bake for 12 to 14 minutes, until the onion is lightly golden, the sausage is golden around the edges, and the drippings or oil are bubbling. Using oven mitts or pot holders, remove the muffin tin from the oven and divide the batter evenly among the wells, about 3 tablespoons of batter for each well. Using oven mitts or pot holders, carefully return the muffin tin to the oven and cook for 18 to 20 minutes, until popovers are puffed and golden brown on top. Using oven mitts or pot holders, remove the popovers from the oven and serve immediately, as they will deflate if you let them sit after baking.
Yield: 12 Sausage Popovers