In a non-stick saucepan combine the wine, onion and garlic; heat to boiling, simmer 5 minutes. Cool, and discard solids. Add the dry mustard to the cooked liquid, stirring constantly until smooth. Blend in honey, oil and salt; heat slowly until thickened (keep nose away; fumes are strong!), stirring constantly. Pour into a glass jar; cool, let sit on counter at room temperature overnight. Refrigerate for 2-8 weeks to age flavour before using.