Prepare the sauce : combine all the ingredients. Refrigerate.
Chop the onion and cook it in olive oil. Cook your steaks too.
Cut the lettuce leaves and pickles into slices. Prepare the burger breads, you'll need 2 bottoms and a top.
Let's make the burger : * Bottom bun * 2 Tbsp Big Mac® sauce * Some onion slices * Some lettuces strips * 1 slice cheddar cheese * 1 beef steak * Bottom bun * 2 Tbsp Big Mac® sauce * Some onion slices * Some lettuces strips * Some pickles slices * 1 beef steack * Top bun
Do the same with the second burger and there you are !