Soak marrow bones in salted ice bath for 24 hours, change water frequently, drain, pat dry.

Season marrow bones with salt, roast on sheet tray at 220°C in oven for 30 minutes or until fully rendered, reserve all fat, discard bones.

Combine all ingredients except egg yolk in saucepan, cook over medium-low heat for about 10 minutes until garlic and ginger are fully cooked, transfer contents to blender.

Blend with egg yolks to emulsify, adjust seasoning as needed, pass through chinois and reserve in siphon for service.