Deflowering Angelica

I purchased an Angelica (archangelica) from you last year. It is beautiful this year. I have 2 questions about it.
1. I think it is in flower; Are the flowers green-ish or will they become more white?

They are greenish white.

2. I know the flowers must be removed in order for the plant not to 'suicide'. Do i cut the stalks from the base of the plant? Or do I cut the flower heads at their base?

Just cut the flowerheads off. The key is to prevent the plant from developing seeds which seems to be a trigger moving the plant into 'suicide' mode.