Remove the peas from the pods, if not already done. Put enough water in a large pot with 1 tsp (5 g) of salt per 4 1/5 cups (1 liter) of water and blanch the peas for 2 minutes, if they are small and for 4 minutes - if they are larger.
Remove the peas and rinse under cold running water. Similarly blanch the chopped onions if you want to use it. Prepare a hot brine by boiling water and salt - 1 1/3 tbsp (20 g) of salt per 4 1/5 cups (1 liter) of water.
Distribute the peas and onions into jars, for 1 jar you will need about 2 1/5 cups (550 g) of peas. Distribute the hot brine into the jars - about 1 1/5 cups (300 ml) per jar.
Close the jars and sterilize 80 minutes for large peas, about 65 minutes for small ones and 70 minutes for medium-sized peas.