1) Place the butter into a large (4 to 6-litre) saucepan over medium-low heat. Once melted, add the onion and a generous pinch of salt and sweat for two to three minutes. Add the garlic and continue to sweat for an additional one to two minutes, making certain not to allow onions or garlic to brown.
2) Add the peas, chicken and curry powder. Increase heat to high and bring to a boil. Reduce heat to low, cover and cook at a simmer until the peas are tender and not holding their shape any longer, approximately 45 to 50 minutes. Taste and adjust seasoning as needed.
3) Using care and a stick blender, puree the soup until the desired consistency. Watch out for hot splatters.