In a medium non-stick pan, heat 2 teaspoons of olive oil on medium heat until the oil is hot.
Add the spinach, season with salt & pepper, and saute until the spinach wilts - about 2 - 3 minutes. STIR FREQUENTLY
When done, transfer cooked spinach to a strainer and strain over the sink or into a bowl as much of the liquid as you can by pressing down on the spinach with a wooden or plastic serving spoon.
Discard the liquid and transfer the spinach to a cutting board.
Finely chop the drained spinach and transfer to a bowl.
Add 4 tablespoons of the minced shallot plus the vinegar to the bowl.
Add the walnuts, capers and Parmesan cheese to the bowl and stir to combine.
Season with salt & pepper to taste.
The goal is to make a rough paste by adding a little olive oil at a time until you have a nice consistency of pesto. You may even want to try using a mortar & pestle or food processor to create an even finer texture.
Your pesto is now ready to serve as a garnish with fish or chicken or you may want to use it in some of your favorite pesto dishes like pasta or salads.