Thaw shrimp in the fridge if needed. If your shrimp are not deveined, use a pair of kitchen scissors or a sharp knife to cut down the back of each shrimp and remove the black vein.
Once the veins are removed, make the slit down the back deeper--cut about halfway down the back of the shrimp, just don't cut it in half.
In a large bowl, mix the water and salt and stir well.
Add the shrimp and let sit in the fridge for 15 minutes.
In the meantime, heat your broiler to high and place your oven rack about 4 inches from the flame.
In a medium bowl, mix the butter, oil, garlic, pepper flakes, anise seed and parsley and stir.
Remove the shrimp from the brine and pat well on paper towels until very dry.
Add the shrimp to the garlic mixture and toss to coat.
Stuff some of the herbs into the cracks along the shrimp's back if you can.
Transfer the shrimp to a rack on a cookie sheet, leaving them enough space so that they don't touch. It's okay to roast them in two batches if needed
Place the shrimp under the broiler for 2-4 minutes, then bring them out, flip them and roast 2-4 minutes more until they are pink throughout. This is not a good time to turn your back on them.
Serve warm or at room temperature.