Sourdough Pizza with Onions and Anchovies

I use the term, "Pizza" rather loosely. There's a bit of cheese, but only about half a cup-hardly any at all by my household's standards. There's a whole hell of a lot of bread though. And onions. The egg was just being silly, though it turned out OK. I don't eat this sort of thing, but as everyone tucked-in and I didn't hear complaints, I'll assume it was good. I hope they liked it as they'll be eating it again tomorrow.

For the Onions:

2 large, sweet onions (about 1 1/2 lbs.) minced
3 tablespoons olive oil
3 cloves garlic, minced
1/2 teaspoon dried thyme
1/4 teaspoon salt
1/4 teaspoon pepper
1 bay leaf
Pinch of ground cloves

Cook all over very low heat until very soft-about 1 hour. remove bay leaf, and chill until needed.

For the crust:

Sponge:

1 cup fed sourdough starter
2 cups water
2 cups strong flour
Mix well. Let stand four to five hours.

Final dough:

To the sponge add:

1 teaspoon instant yeast (you can skip this, but it will take longer)
1 tablespoon granulated sugar
2 teaspoons salt
Enough plain flour to make a dough that is tacky but not soaking wet. Mix all together and cover with cling film in same bowl. Let stand 30 minutes.

After 30 minutes, knead dough adding flour if needed to keep it from sticking-only add what you absolutely need. Cover and let rise until doubled.

Stretch out dough and place in a very well oiled pan. Preheat oven to 450 degrees F. If you are doing a heavy topping, it helps to pre-bake the crust for 20 minutes. Remove crust from oven and add toppings. Return to a much hotter oven-around 475-500. Bake until topping is nicely browned. If doing an egg, add it in the last even or eight minutes.