Place garlic on a sheet of tin foil, drizzle with 1 tsp olive oil. Fold foil tightly around garlic.
Bake at 425 until garlic head is soft, about 30 minutes. Remove from oven, allow to cool.
In a saucepan over medium heat, add the remaining oil and the onions. Cook until onions have started to soften. Add ¼ cup porter beer, cook over medium/low heat until beer has reduced and pan looks dry, about 20 minutes. Repeat with the remaining ¼ cup porter beer.
Once the onions are a dark amber color and pan looks dry, remove from heat.
Add the Greek yogurt, Worcestershire sauce, salt, pepper and onions to a food processor. Gently squeeze the garlic until the soft cloves protrude. Add the cloves to the food processor, discard the rest of the head. Process until smooth.
Chill until ready to serve (dip has the best flavor the day after it’s made).
Top with chives prior to serving
Notes
For added flavor (and added calories) and 4 oz cream cheese to the food processor in step 6.