Portugal's quintessential tavern petisco: tender strips of beef tenderloin flash-fried with garlic and bay, braised in a savory beer, butter, and mustard sauce, topped with pickled vegetables and olives.
Heat olive oil and half the butter in a skillet over high heat. Sear beef strips for 2 minutes until browned on the outside while pink inside. Remove beef to a plate.
In the same pan, add garlic, bay leaves, and piri-piri. Pour in beer and vinegar, scraping up pan fond. Whisk in mustard and remaining butter, boiling for 2 minutes to reduce into a glossy sauce.
Return beef strips to the sauce for 30 seconds to reheat and coat in the savory pan sauce.
Scatter chopped pickled vegetables and black olives over the meat. Serve with toothpicks (pica-pau) and crusty bread.