How to add an optional toppings option to Woocommerce products?

I want to add an optional topping feature to my Woocommerce wordpress food joint site. I have a pizza category and every pizza has three different sizes. Though I can add the toppings with fixed price, but I want to let the users add as many toppings they want and the price for the toppings changes with the size of the pizza. It has been done on several sites and here are two example sites I could found.

https://www.cavallinofrankfurt.de/pizza/
pizza.de

I am using the composite product woocommerce extension but don’t know how to use it to get this. Have tried several things, but it doesn’t seem to work exactly how I would want to it to, i.e. different topping prices for different sizes. I have about 20 toppings to offer.

Please help.

Here is my site – https://www.pizzamanhattanffm.de/