Peel and seed pumpkin and cut into 1" cubes.
Melt butter in large pot, add onion and garlic and cook over med-low heat until transparent.
Add pumpkin cubes and toss with onion, cook 2-3 minutes.
Add water and bouillon cubes, bring to a boil.
Immediately add salt, pepper, ginger, bay leaf, lemon juice, orange zest, then reduce heat to simmer.
Gently simmer over low heat, mostly covered for 20 minutes. Stir occasionally.
Remove from heat. Discard zest and bay leaf. Cool soup slightly.
Process with handheld food processor (keep blade at the bottom of pan to avoid hot splatters)
Remove 1/2 cup soup, and blend with milk and sour cream. Gently add back to the rest of soup, stirring constantly so cream does not curdle.
Reheat gently before serving. Do not let come to a boil again.
Garnish with snipped green onions and a dollop of sour cream!