Melt 2 tablespoons butter in a saute pan over medium-high heat.
Add chopped mushrooms and saute until browning, about 5-8 minutes. Set aside.
Prepare the oysters
Chop the oysters into small pieces. (If using large pastry shells, leave about 12 smaller oysters whole).
Add the chopped oysters and all the juice to a saucepan; bring to a simmer and maintain for 10 minutes. Strain oysters, reserve liquid.
Prepare the Pastry Shells
If using frozen pastry, prepare them according to the package instructions. If using fresh pastry, skip this step.
Line a baking sheet with parchment paper. Place the prepared pastry shells on the baking sheet with some space in between the shells. Set aside.
Preheat the oven to 375 degrees Fahrenheit.
To make the filling
Melt 4 tablespoons butter in a saute pan over medium-high heat.
Add the onions and saute until starting to clear about 5 minutes. Stir often so the onions do not brown.
Add the sauteed mushrooms (with any juice) and mix to blend. Stir for about 5 minutes.
Add the AP flour and stir to mix it into the onions and mushrooms completely.
Add the Herb and Spice Blend, mix well, and continue to stir for about 3 minutes.
Warm the whole milk in the microwave or stovetop. Add the milk a little at a time, stirring to thoroughly combine with the veggies.
Once all the milk has been added, bring it to a simmer and maintain that, stirring often, until starting to thicken about 5 minutes
Drain the oysters, reserving the liquid. Add the oysters to the sauce and blend well. Continue to simmer. Add the Worcestershire and Tabasco and continue to simmer for a couple of minutes.
Add some of the reserved oyster juice until you have the consistency you want.
Add parsley and pimentoes (if using). Mix well and set aside.
Fill the Pastry Shells and bake
If you haven't already done so, place the prepared patty shells on a large, parchment paper-lined baking sheet. Make sure to leave space between each pattie.
Use a spoon to fill the patty shells with the oyster mixture. For larger puff pastries, place a couple of the reserved whole oysters in each pastry.
Place the baking into the preheated oven and bake for about 20 minutes or until the pastry is starting to brown and the filling is bubbly.
Take out, top with finely green onion tops. Set aside and let cool for about 5 minutes.
Notes
This recipe will yield about 12 large puff pasties or 36 small pastries. The nutritional information is estimated using large pastry shells.If you are going for the smaller pastry shells (bouchée), chop the oysters. If using the larger shells (vol-au-vents), you can use whole oysters or a combination of chopped and whole.This recipe can be made with turkey or chicken instead of oysters. Use about 2 cups of chopped turkey or chicken and make sure to have some chicken or turkey stock handy if you need to thin the sauce. You can also make this with all mushrooms. Use about 4 or 5 cups of mushrooms and chicken or vegetable stock to thin the sauce, if needed. Don’t fill the shells too early or they will tend to get a bit soggy. If you have leftover filled shells, store them in an airtight container in the fridge for 3 to 4 days. Pull the leftover shells out of the fridge about 1 hour before reheating. Reheat, uncovered, in a 350 degree Fahrenheit oven until warmed through (about 10-15 minutes). Shells may get soggy after a while, so it's best not to fill more shells than you will be serving. You can keep the sauce refrigerated in an airtight container, then when you're ready to serve, just fill the pastry and follow the instructions to finish.The filling can be frozen for up to six months in an airtight container. Defrost in the fridge overnight, then fill pastry shells and finish according to the instructions. With the butter and milk you may experience some separation in the sauce, but just gently stir it back together as you reheat it on the stove.You can make the sauce in advance up to the point of adding the oysters. Keep everything refrigerated in an airtight container. When ready to serve, start at the step of adding the oysters and finish it out. It's also possible to make the sauce to completion and then simply stuff the shells prior to baking.