Too many toppings on a pizza is a question of water, fat and weight more than of number. The base has to dry out and hold up in the time the crust takes to bake, so two wet toppings can sink a pie that four dry ones would not. The useful question for each extra topping is what it adds to that load, and whether the oven can deal with it before the base is done.
Where the load comes from
Water is the first load. Raw mushrooms are about 92 percent water and raw tomatoes about 94 percent, and water trapped under a lid of melted cheese has nowhere to go but down into the dough. Every wet topping laid on top of the first one adds to the same puddle. The cheese counts too: fresh mozzarella carries far more water than the low-moisture block, as set out in mozzarella by moisture level.
Fat is the second. Pepperoni, bacon and sausage render as they cook. Fat softens a crust less than water does, but three rendering meats on one base run towards the centre and pool there.
Weight is the third. A heap in the middle sits on the part of the base that sets last, and a thin base has little crumb to hold it up.
What each kind of topping brings to the base
| Topping | What it adds | How to lower the load |
|---|---|---|
| Raw mushrooms, courgette, fresh tomato | Water, released in the oven | Cook mushrooms down in a dry pan; salt and drain courgette and tomato slices |
| Fresh mozzarella, ricotta | Water | Drain torn mozzarella; use ricotta in spoonfuls with gaps between them |
| Pepperoni, sausage, bacon | Rendered fat | Spread them wide, and use less of each when you stack them |
| Jarred artichoke, roasted peppers in oil, olives | Brine or oil | Drain and pat dry |
| Rocket, basil, a drizzle | Nothing to the bake | Add after the pizza comes out |
Onions sit in the first row when they go on thick and raw. Sliced thin or cooked first, they lose most of their water before they reach the dough, which is the case made in cooking onions before they go on.
Toppings that do the same job
Flavour has its own ceiling. When two toppings do the same job, the second adds load and very little taste. Pepperoni, sausage, bacon and meatball are four toppings and one idea: salt and rendering pork. Pepperoni, pickled chilli, red onion and basil are four toppings doing four jobs: salt and fat, acid, sharpness, and something fresh added after the bake.
Cutting works the same way in reverse. Take away the topping whose job another one is already doing, and the base has less to carry while the pizza tastes of the same things.
Carrying more on one pizza
Split the pie. Two halves with their own toppings each carry half the load, and the pizza tastes like two different things.
Choose a base built for weight. Pan and deep-dish pizzas have thicker dough and a longer bake, so they carry more than a thin base can.
Keep the sauce thin. An even layer that still shows the dough at the edges is enough, and extra sauce is extra water sitting directly on the base.
Layer with intent. Sauce, then cheese, then the heavy toppings spaced apart on top, then anything delicate after the bake. Pepperoni on top of the cheese crisps and cups. Pepperoni buried under it steams.
Keep the wettest toppings away from the centre, the part of the base that sets last. When one topping has to go, dropping the wettest one or cooking it down first takes the most load off the base, and the cured meats and the finishing herbs can stay as they are.