1 12-oz. bottle or can of ginger ale (such as Seagram's)¼ cup yellow mustard
2 Tbsp. Dijon mustard
½ Piece ginger, peeled, finely chopped
3 Garlic cloves, finely chopped
½ Cup grated sweet onion
3 Tbsp. honey
1 Tbsp. granulated sugar
2 Tbsp. Diamond Crystal or 1 tsp. kosher salt
1 Tbsp. apple cider vinegar
½ Tbsp. coarsely ground black pepper
¼ Tbsp. crushed red pepper flakes
Step 1: Whisk ginger ale, yellow mustard, and Dijon mustard in a medium saucepan to combine. Bring to a simmer over medium heat; reduce heat to low and gently simmer 3 minutes. Whisk in ginger, garlic, onion, honey, sugar, salt, vinegar, black pepper, and red pepper flakes and cook, stirring occasionally, until flavors have come together and sauce is very fragrant, 15–20 minutes. Let cool before using.
Do ahead: Sauce can be made 2 days ahead. Transfer to an airtight container; cover and chill.