Sauté onions in the oil in the pressure cooker for approximately 3 minutes, or until they begin to soften, but not browned.
Add remaining ingredients, except half & half, maple syrup and salt.
Lock the lid in place and bring to pressure, then lower heat and cook for suggested time. Allow pressure to drop by the quick release method or automatic release method, remove the lid and allow to cool slightly.
Place ingredients into a standard blender or food processor, or use a handheld immersion blender, along with half & half, maple syrup and salt, if desired.
Puree until smooth. Serve medium hot. Top with a bit of grated cheddar cheese.
Suggested time for fast 15 psi pressure cookers: Cook for 10 minutes on high pressure.