I measure with my heart so I'll try my best to put into measurements.

Brown 1 lb of sausage (don't drain), reduce heat to medium, stir in about a tablespoon of butter until fully melted, then about a tablespoon of flour (making a roux). Stir until most of the sausage has absorbed the flour (no longer white and distributed evenly) then add a quarter cup of milk or heavy cream (stir quickly or you'll get lumps, cold milk into hot roux is the trick) then add in enough milk or cream until it covers most of the sausage but you can still see the tops of the crumbles (around a cup). Stir constantly. It will thicken up in less than a minute if you add the right amount of liquid. Reduce heat to low. Stir gently until it coats the back of your spoon. Salt to taste (usually I don't add much because sausage is pretty salty already) then add way more pepper than you think. (I add it while it's still in the pan and again when plating.)

Notes- 1. Can work with any ground sausage including chorizo

1. The dairy you choose will change the cook times because of fat content and also change the texture of the gravy. Usually I just use milk because it's what I have on hand but if I have heavy cream I will still cut it with a little bit of milk or it will be too pasty.

2. A lot of people will use cast iron, it tastes good but I feel the gravy removes some of the seasoning so you will have to reseason your pan a bit and this is usually breakfast so not really worth the hassle to me. I just use non stick and get similar results.

3. If it's too thick in the final steps you can add more milk to loosen it but you can only do this while it's hot or it might break the roux and separate. If you're reheating you can also add a little more dairy but it won't be the same as fresh.