Steps
1. Soak the sweetbreads in cold water with a pinch of salt for 2 hours, changing water once.
2. Drain and blanch sweetbreads in simmering water for 5 minutes, then shock in ice water.
3. Gently remove any membranes or impurities from sweetbreads and pat dry.
4. For the ajo blanco sauce, soak bread slices in cold water for 5 minutes, then squeeze out excess water.
5. In a blender, combine soaked bread, almonds, garlic, cold water, olive oil, sherry vinegar, salt, and white pepper. Blend until smooth and creamy.
6. Strain the sauce through a fine sieve and chill.
7. Heat a pan with a mix of butter and olive oil over medium-high heat.
8. Season sweetbreads with salt and pepper, then sear for 3-4 minutes per side until golden and crisp.
9. Plate sweetbreads atop a generous spoonful of ajo blanco sauce.
10. Garnish with chopped fresh parsley and serve immediately.