Toast almonds in a wide frying pan over medium-low heat, stirring frequently, until lightly browned; turn out of pan and cool.
Using metal blade, process garlic until chopped.
Cut onion in chunks, add to garlic, and process with on-off bursts until onion is chopped; set aside.
Break mushrooms in half if large, drop in processor bowl, and process with on-off bursts until coarsely chopped.
Melt butter in frying pan over medium-high heat.
Add garlic, onion, mushrooms, salt, thyme, and pepper.
Cook, stirring occasionally, until most liquid has evaporated.
Process almonds until coarsely chopped.
Remove 2 tablespoons nuts and set aside.
Process remaining nuts to form a paste.
Pour oil down feed tube and process until creamy.
Add mushroom mixture and process until pate is smooth.
Add reserved nuts and blend with 2 on-off bursts.
Cover and chill if made ahead.