First you need to make sure that the cake will actually come out of the ramekins. You do this by buttering the ramekins and then adding a little bit of flour so it's coated. Tap against your hand to remove excess flour. You'll know the lava cake is down when the edges are firm, but it's still slightly jiggly in the center. Luckily with the ganache, even if you over bake it, the ganache will still ooze out.