Preheat oven to 450 degrees. If using a convection over, preheat to 400.
In a 30cm paella pan (recipe can be doubled in a larger pan), make a sofrito by heating the the olive oil over medium heat and adding onion and garlic.
Season the onion and garlic with a generous pinch of salt and cook until translucent.
Add tomatoes and cook until the tomatoes begin to dry out and form a residue.
Add the saffron and pimeton, lower the heat and briefly stir to incorporate.
Add the diced chicken meat and stir well over medium heat.
Add the bomba rice and stir to coat thoroughly with the sofrito.
Raise the heat to high and add the warm stock. Taste and adjust the seasoning by adding salt. As rice is not stirred during cooking, it’s important that the seasoning be correct at the point. It should taste well seasoned but overly salty.
When the paella reaches a boil, add the sprig of rosemary and butter beans and cook on the stove for 5 minutes.
Place paella in preheated oven.
After 5 minutes, add the shrimp.
After 3 minutes, add the clams hinge side down. Do not overcrowd the clams so that you can give them room to open.
Cook for an additional 5 minutes.
If there is any additional liquid, place the plan over high heat on the stove to remove any additional liquid.
Allow the paella to sit for 5-10 minutes before serving.