Add the flour and salt to the bowl of your food processor (or a large bowl if you're making the dough by hand).
Turn the food processor on low speed. Add the chunks of cold butter one at a time while the food processor runs until all the butter is added and the mixture resembles coarse crumbs.
If making by hand, use a pastry blender or your hands to work the butter into the dough until the mixture is crumbly. Try not to handle the butter too much (the heat from your hands will soften it) – use quick movements and don't worry if some larger chunks of butter still remain.
Add the vinegar and the water slowly as the food processor runs on low, just until the dough comes together and pulls away from the sides of the bowl. Depending on the weather and even on the brand of flour, I use anywhere between 3 and 5 tablespoons of water.
If making by hand, use your hands to form the dough gently and quickly using just enough water for the dough to come together.
Dump the rough dough onto the counter. Divide the dough into a disc shape and wrap it in plastic wrap, placing it in the fridge to chill for 45 minutes or overnight.
Preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius).
Remove the chilled pie dough from the fridge and let it sit for about 10 minutes before rolling.
Roll out the disk of dough into a large circle using a rolling pin. Add a generous amount of flour to the rolling surface and to the rolling pin, to prevent sticking and cracking.
Peel the rolled out dough off the counter surface gently by rolling it backwards onto the rolling pin. Transfer it to a 9-inch pie dish and gently press the dough into the bottom of the pie dish and over the edges (try for a 1-2 inch overhang if possible).
Roll the edges back onto themselves, pierce the dough with a fork over the whole surface and blind bake for 20 minutes. If you have pie weights, feel free to use them.
While the pie dough bakes, cook your bacon in a pan, let it cool, and chop it.
Crack the eggs into a bowl, add the sour cream, salt, pepper, and garlic powder.
Whisk the eggs, sour cream, and spices together, until the mixture is smooth and well combined.
Add the shredded cheese (reserve about 1/4 cup for the top), the bacon, and the chopped up fresh herbs (if using). Stir in gently until combined.
When the pie crust is done blind baking, remove it from the oven and lower the oven temperature to 350 degrees Fahrenheit (175 degrees Celsius).
Pour the mixture into the warm pie crust and top with the remaining shredded cheese.
Bake at 350 degrees Fahrenheit (175 degrees Celsius) for about 30-35 minutes, or until the top is golden brown and there's only a very slight jiggle in the centre.
Remove the quiche from the oven and let it cool for at least 10-15 minutes before slicing and serving with some chopped chives.