Melt Horio soft unsalted with cow butter in a pot over medium heat.
Add celery, onion, cover and cook until softened, for about 10 minutes.
If vegetables start getting brown, add water.
Pour sour milk in the pot and simmer, mixing occasionally, until mixture thickens, for 5 minutes.
Remove from heat and let cool.
Add mustard, pepper, ½ tsp salt, ¼ tsp white pepper in the cold mixture and mix well. Add egg and crabmeat. Mix tenderly.
Put breadcrumbs in a shallow plate and spread evenly.
Take a portion in your hands and press softly to remove liquids. Make a small meatball. Mixture should be relatively soft and moist.
Cover meatball with breadcrumbs on every side and place on a platter. Repeat with rest of mixture, unlit you have 12-14 meatballs.
Cover and refrigerate for at least 1 hour to 3 hours max.
Melt 1 tbsp butter and 1 tbsp olive oil in a pan over low to medium heat and add crab meatballs. Fry from one side for 5-6 minutes and then turn for 4-5 minutes. Keep them warm when removing them from pan.