I am not an expert at making paella by any means, but this is how I make it.
I never use store bought stock unless I have no option. I usually have the freezer full of bags of chicken bones that I save, but not this time, so I used a full chicken.
I don't use the breasts for the stock, since they don't give out that much flavor. To remove them from the carcass, it's best to first remove the wish bone, then make a couple of cuts at the center on each side of the breast bone and simply pull from the breast fillets. You only need to make a couple of cuts through joints to debone a chicken, most of it is twisting and pulling. I chop it all in small pieces and roast it in the oven until it's well browned.
I throw it in a pressure cooker with a couple of celery ribs and two or three large carrots and one onion, which I first cook for 5 minutes with a bit of oil. Then cover it with filtered water and cook at 15 psi for 1.5 hours. Once finished, cool the pressure cooker in the sink with cool water and strain the stock.
I don't put any herbs or spices on my stock, it's a very simple stock. If I need any extra flavors I add these later once I use the stock in a dish that needs that flavor.
I found a brine recipe in a magazine once and I never make chicken without brining it this way. It makes it very juicy and perfectly seasoned. Use 1 cup of salt, 1 cup of sugar and 4 quarts of water and brine the chicken for 45 minutes, then dry, cut in bite size pieces and save in the fridge.
I like to have all the ingredients ready to go before I start.
First brown the chicken at high heat with olive oil, then remove from the pan and save.
Then make the sofrito. I used 1 green pepper, 1 red pepper, 1 yellow onion and 4 garlic cloves. Once all the vegetables are soft I add one can of tomatoes and cook it longer. The secret for a good sofrito is a lot of patience.
Once the sofrito is ready I add the fish and the chicken, and also paprika, saffron and a yellow food coloring that they sell in Spain special for paellas.
Then add the rice, and cook it for 2 or 3 minutes. I use 1 kilogram of rice for this paella size. Bomba rice is the best.
Finally add the stock, about 200 ml per each 100 grams of rice, so in this case, 2 liters. I usually save some extra in case I need it later.
Now raise the heat until it starts boiling then lower it and let it cook at medium low until the rice is almost done.
It's very important to not stir the rice at this point. If you do this at a party, someone will come and undoubtedly grab your spoon and try to stir it. Don't let them.
Raise the heat for the last 5 minutes and add the extra toppings, in this case I used green beans but you can use shrimp or mussels or whatever you like.
Cover with aluminum foil for at least 15 minutes and let it rest before serving.