Peel and roughly chop the onion and garlic and place in a non-reactive saucepan. What is a non-reactive saucepan? It's a saucepan made of a material that will not react with acidic ingredients. For example, stainless-steel is non-reactive, whereas copper is a reactive material that will esily become worn off if used with acidic ingredients (lemon juice, vinegar, etc.).Pour in the white wine, white wine vinegar and water and bring to boil over medium heat. Simmer for just about 5 minutes.Cool, strain and discard the solids.Place the mustard powder into a saucepan and add the strained liquid. Mix until well combined. Cook over low-medium heat until it thickens.Add stevia (if used), extra virgin olive oil and season with salt. If you're making Dijon mustard, also add the turmeric and tabasco and blend in well.Place in a jar and keep refrigerated for up to 6 months. The mustard will taste best after a few weeks of "ageing".Instead of 1 cup of mustard powder, use just half of it.In a blender, roughly chop the mustard seeds. Do not over process.Follow the same steps as for the yellow / Dijon mustard. Again, you will need to keep the mustard in the fridge for about 2 weeks before it's ready.