Add a greased or Silpat lined sheet pan to your oven on its lowest setting. Mine is 150 F (65 C). 

Drain 3 tablespoons of canned peas and give them a rough chop just to break up some of the peas. 

Add water to a medium-sized pot and bring to a simmer. Add sodium citrate and stir to combine.

Slowly add all the shredded cheese, stopping to stir the cheese into the sauce after every handful. Once all the cheese is added stir very well while the cheese is still simmering to make sure it is very smooth. Add the peas and stir until they are fully incorporated in the sauce.

Once the peas and cheese mixture is very smooth, carefully pour the sauce over the warm sheet pan and shake the sheet pan to allow the sauce to spread out. You may need a knife or offset spatula for this. 

Cover the cheese with parchment or wax paper, press down with your hands to flatten the cheese sauce, and move the pan to a refrigerator to cool for around at least an hour.

Once the peas cheese is fully cool, you can carefully remove it from the sheet pan and slice the cheese into 3.5-inch squares or whatever shapes you desire. To store the cheese, place a piece of parchment or wax paper between each slice and store it in the refrigerator for up to three weeks.