In a medium saucepan melt the butter over med/low heat.
When melted, add the onion and cook until the onion is tender, but not browned, approximately 3-4 minutes.
Add the flour, salt and pepper. Let the flour cook for at least a minute to burn off any raw flour taste. Add the chicken base and stir to combine.
Slowly add 1 cup of the warmed milk and all of the heavy cream, stirring constantly.
Once all the ingredients of the soup are combined, add the crab and cook on low for 5 minutes until thick, stirring often.
Add the remaining ½ cup of milk and the sherry and slowly stir to warm through.
Serve warm or hot in a bowl with a side of oyster crackers
