Cut the avocado in half, remove the pit and scoop the flesh out into a medium bowl. Use a fine grater to shred the garlic clove into the bowl. If you want the guacamole super spicy, add more garlic.
Smash the avocado and garlic together with the back of a fork until smooth. Add the yogurt, salsa, lime juice, tomato, onion, jalapeño and a pinch of salt and pepper. Mix together, taste and add more lime juice or salt as needed.