Add the prawn heads and peels to a medium-sized pot and cover with 4 cups water. Season with salt and pepper. Bring to a boil over high heat and then turn it down to a slow simmer. Press down on the prawn heads and peels as it simmers away to extract as much flavour as you can. Leave it to simmer for about 30 minutes. Strain the shells and place the stock in a bowl.
Heat the olive oil in a stock pot over medium-high and add in the pork mince. Cook until browned. Add the onions and cook for 5 minutes until transparent. Add in the garlic and cook until golden brown. Add in the firm tofu and saute for a further 5 minutes.
Pour in the prawn stock reserving ¼ cup. Bring to a slow boil. Meanwhile add in the achuete and arrowroot into the ¼ cup of reserved prawn stock and mix well making sure there are no lumps. Add into the sauce and keep stirring until thick.
Season with the fish sauce and leave to simmer for a further 30 minutes to develop more flavor. Just before serving taste and season more with fish sauce and salt and pepper.
Take the Yuba sheets out of the packet unfold the sheets and cut into thin ½ cm strips on the long side. Rinse in cold water to separate the noodles and then quickly saute them in some olive oil for 5 minutes to heat through.
Note: You can prep the Yuba sheets the day before and keep them in cold water in the refrigerator and then drain and dry them before the quick saute.
Ladle the sauce in a bowl and lay out the noodles around the bowl. Arrange the prawns, quail eggs, chicharron, tinapa, lemon wedges or kalamansi and green onions around the sauce and noodles so each guest can make their own mix.
Note: The prawn stock can be made a week ahead and kept in the freezer until you make the sauce.
The sauce can also be made a 2-3 days ahead and kept in the refrigerator and reheated until serving.
To poach the prawns fill a large pot with water and season with 1 Tablespoon of salt. Add in the prawns and cook for 5 minutes until they start to curl and turn pink. Take out of the water.