Preheat your oven to 375 if you are baking gluten free, 400 if you are using traditional all-purpose flour. Grease a small 8x8 baking dish.
While you are prepping your biscuits, place a foil lined baking sheet in the oven with bacon covering it in a single layer. The bacon will take about 40 minutes to bake. Remove when it's your desired level of crispiness. I like mine crispy so I sometimes leave it for 45-50 minutes. It also depends on how thick cut your bacon is. Less thick, less time, etc.
IMPORTANT: When you remove your bacon from the oven, immediately transfer it to a paper towel lined plate, or the juices will go back into the bacon and it will be overly greasy and heavy. Allow the bacon to drain on the plate, and then transfer 1/4 cup of the excess fat/juices from your lined baking sheet, to a pan on the stove for your bacon gravy. See instructions for gravy below.
Beat the egg into the sour cream. Mix all the dry ingredients in a separate bowl, and then mix them into the sour cream egg mixture. Stir until just mixed, over mixing will make a tough biscuit. Toss the dough out onto a lightly floured surface. With your hands shape the dough into a square roughly the size of your baking dish, and about 1 1/2" high. Cut into 9 squares. Place dough pieces side-by-side int the baking dish. Bake for 15-20 minutes at 400, or til golden brown on top, if you are using traditional all-purpose flour. Alternately, bake for 20-25 minutes, or til golden brown on top, if you are using a gluten free measure for measure blend.
Once your bacon is done, and you have transferred the fats from the baking sheet, to your stovetop pan, you will now need to make a roux.
You only need a couple tablespoons of the fat from the bacon, to make a roux that yields about a cup of gravy. If you are making a larger portion, just up the ratio: 2 T fat, 2 T flour, to one cup milk. For this recipe I make a 2 cup yielding gravy, using 1/4 cup flour to 1/4 cup fats, to 2 cups milk.
To make a roux, using a whisk, fork or potato masher, whisk together the fats and flour until smooth, while heating on medium to medium low heat.
Next, add your milk, and again stir frequently to keep it smooth.
Add a pinch of salt and a pinch of pepper, stir and taste. Add more salt and/or pepper as needed, to taste.