Using your paella pan, heat the olive oil over medium-high heat. Add in the onions and sauté until softened, for about 3 to 4 minutes. Stir in the garlic and continue to sauté until fragrant, for about 1 to 2 minutes.
Add in the squid and toss and cook in the pan with the onions and garlic for about 1 to 1 1/2 minutes only. Squid cooks very fast. Anything too long and it will become too rubbery. Two minutes over high heat is plenty. Next, remove all the squid from the pan and onto a plate. You will add back into the pan at the end. Cooking it at the beginning adds a little flavor to the onions and oil.
Add in the tomatoes and tomato paste, mix together and season with some salt and pepper. (For the saffron: get a 1/2 cup of water and add in the saffron. This helps to loosen the saffron when it enters the paella and will help it spread better throughout the paella to give it better color.) Add in the smoked paprika into the pan and pour the saffron water all over, mixing well, and cook for about 4 to 5 minutes. While that is cooking, using a separate small saucepan, bring the chicken stock and wine to a low simmer. Alternatively, you can add directly into the pan but simmering separately first and then adding is preferred.
Next, add in the rice into the paella pan and stir well until all of the grains are coated with the tomato sauce mixture and the rice is evenly distributed around the pan. Gently add the simmering stock and white wine mixture to the pan evenly over the rice. Turn up the heat to medium high and bring to a light boil, and season with more salt.
Once it starts boiling, turn the heat down to low and let the rice simmer for about 15 to 20 minutes. If it looks like you need more liquid to help your rice cook, you can add just a little more chicken stock to the rice, half way through cooking. If you do this, pour evenly over the rice and then make sure the rice is still evenly distributed over the skillet.
As your paella is cooking, remember to keep mixing around the pan (from the outside in) so it doesn't stick to the bottom as much. A little sticking is ok (and some people really enjoy the really cooked bits stuck to the bottom) but you just don't want it to burn. While the rice is cooking, prepare the mussels.