In this Instructable, I will show how to make your gravy come out very smooth and how to sneak in a bit of nutrition, while you're at it.
Step 1: Gravy - Preventing the Lumps
There are a few things to bear in mind when cooking a gravy, however, that pretty much always applies.
1) If your recipe calls for browning the flour (such as for a brown gravy), the best two tools to use are patience and vigilance. You will need to keep stirring / folding the flour around as the temperature slowly rises. Flour doesn't brown until it gets to a certain point, but when it does, the browning process is rapid. You will need to watch it carefully, and just keep moving the flour so that all of the flour gets the same amount of time on the bottom of the pan and, hence, all of the flour heats up at the same time. Once the gravy starts browning, this process becomes even more urgent; you want to keep folding the lighter flour down to the bottom of the pan, so that the flour all browns to the same color.
2) For avoiding the creation of unwanted lumps, the most crucial point in the gravy making process is when you add water. When water comes into contact with flour, it creates a sort of paste which is fairly water-proof. If a "ball" of flour gets wet on the outside, the dry flour contained inside this ball of wet flour won't get wet and will remain as an unwelcome surprise when someone goes to take a bite of your gravy. Yech! To avoid these balls of dry flour, add your water slowly, mixing the water in with the flour before adding more water. Also, don't pour the water on top of the flour. Instead, if possible, clear an area so that you can pour the water so that it touches the pan, rather than the flour, then concentrate your mixing at the area where the flour meets the water.
Step 2: Gravy - the Chef's Secret
Step 3: Gravy - Removing the Lumps
There are a few ways to remove the lumps after the gravy is cooked. The first way is to simply pour your gravy through a strainer. This will catch the lumps, removing them from your gravy. However, the problem isn't that the flour is there, but that the flour is in lumps.
I suggest throwing your gravy in a blender and reducing the lumps to just another ingredient in your ultra smooth gravy. Personally, I actually use a Ninja Master Prep food processor (the original, not the Ninja blender) to get rid of any remaining lumps. This does an amazing job, and we have gotten several compliments on the gravy, specifically, at multiple Thanksgiving dinners when we use this method.
NOTE: Be familiar with your kitchen equipment and don't attempt to do this when your gravy is too hot. You don't want to melt your blender's plastic or - worse yet - seriously scald yourself.
Step 4: Adding in Some Nutritional Value
In addition to blending the gravy to ensure that it's smooth, you can also add cooked-down veggies to the blender, as well, to add some nutritional value and to thicken the gravy a bit.
In these pictures, I am adding in cooked carrots into gravy taken from a pot roast my wife made. As you can see, the carrots didn't get completely "smooth", but, when we do this with a turkey gravy, the cooked onions, garlic, celery and parsley blend away to nothing but flavor... and make the gravy a bit thicker, as well.