Pat the shrimp very dry with paper towels, then toss them with the salt in a bowl. Slice the garlic, chop the parsley, and slice the bread.
Pour the olive oil into a 10-inch / 25 cm cazuela or cast-iron skillet and add the garlic and guindilla. Set the pan over medium-low heat and cook for 3 to 4 minutes, until the garlic edges turn pale gold and the oil sizzles gently. If the slices darken faster, lift the pan off the heat for a moment.
Raise the heat to medium and add the shrimp in a single layer. Cook for 1.5 to 2 minutes, until the undersides turn pink, then flip each one and cook another 1.5 to 2 minutes, until opaque and curled into a loose C (145 F / 63 C).
Pour in the sherry and swirl the pan for about 30 seconds, until the sharp alcohol smell fades. Take the pan off the heat and scatter the parsley over the top.
Bring the pan straight to the table and serve within 5 minutes, with the bread alongside for dunking in the oil.