Preheat the oven and bake 4 puff pastry shells according to the package instructions.
In a skillet, sauté 1 garlic clove and 1 small shallot. Add 7 oz small peeled shrimp and cook for about 1–2 minutes until fragrant and the shrimp are just cooked. Season with salt and pepper. Set aside.
In a saucepan, melt 1 tablespoon butter over medium heat. Stir in 1 tablespoon all-purpose flour and cook for about 1 minute to form a roux.
Add 1 teaspoon Dijon mustard and gradually whisk in ¾ cup fish stock , a little at a time, until a smooth sauce forms.
Let the sauce simmer gently until it thickens.
Stir in the shrimp mixture and warm through briefly.
Add most of the 2 tablespoon fresh parsley and adjust seasoning with salt and pepper.
Spoon the shrimp ragout into the warm pastry shells and garnish with remaining parsley.