Set a medium saucepan or pot over high heat and add the onions, wine, vinegar, garlic, peppercorns, rosemary and salt. Bring to a boil and simmer with the lid for 20’ while stirring occasionally.
Remove from fire and pass through a sieve into a glass bowl while throwing away the remaining solids.
Add into the bowl the crushed or grinded mustard seeds and stir. Cover with plastic wrap and leave for 24 hours at room temperature.
Next day add the mixture into a blender or fast-speed food processor with the blade on. Add the turmeric, wheat flour, the optional paprika, sugar and add as much water as needed to achieve a consistence similar to a baby cream.
Pour the blended mixture into a medium saucepan and over medium heat bring to a boil and simmer for 5’.
Remove from fire and add the mustard into glass jars of about 200 ml.