Fried Onion Dippers with Balsamic Ketchup

Ingredients

• 0.3 cup balsamic vinegar 
• 0.1 teaspoon ground pepper 
• 1.3 cups seltzer water 
• 1.5 tablespoons t brown sugar dark packed
• 1 teaspoon ground mustard dry
• 1.3 cups flour all-purpose
• 2  garlic clove minced
• 0.1 teaspoon ground allspice 
• 0.1 teaspoon ground cloves 
• 2 cups catsup 
• 1 tablespoon olive oil 
• 0.5 teaspoon salt plus more for sprinkling
• 1 quarts vegetable oil 
• 1.3 pound onion sweet

Equipment

• bowl
• baking sheet
• paper towels
• sauce pan
• oven
• whisk
• pot
• kitchen thermometer
• aluminum foil
• slotted spoon

Directions

1. Cook garlic in oil in a 2- to 3-quart heavy saucepan over medium heat, stirring, until golden, about 1 minute.
2. Add vinegar and boil over medium heat until slightly thickened, about 2 minutes.
3. Stir in ketchup, sugar, mustard, cloves, allspice, cayenne (if using), and salt and bring to a boil, then reduce heat and simmer, stirring occasionally, 5 minutes, until it's thick and well blended.
4. Transfer to a bowl and let cool to room temperature.
5. Heat oven to 200°F.
6. Whisk together flour, club soda, and salt in a bowl until smooth. Trim both ends of onion and then peel it. Halve onion lengthwise, then cut lengthwise into 3/4-inch-wide wedges. Separate wedges into pieces.
7. Heat 2 inches oil in a 4- to 5-quart heavy pot over medium heat until it registers 365°F on thermometer.
8. Working in batches of about 8, toss onion wedges in batter until coated. Lift onion pieces out of batter one at a time, letting excess batter drip off, and carefully transfer to hot oil. Fry onion dippers, turning with a slotted spoon, until golden, about 2 minutes, then transfer with slotted spoon to paper towels to drain. (Return oil to 365°F between batches.)
9. Sprinkle dippers with salt while still hot and keep warm on a rimmed baking sheet in oven until all onions have been fried.
10. •The balsamic ketchup keeps chilled in an airtight container indefinitely. It can be used in place of regular ketchup.•Like all fried foods, the onions are best when eaten soon after frying, but leftovers can be cooled completely, then arranged in one layer in disposable pans lined with several layers of paper towels, and loosely covered with foil. Chill overnight, then arrange dippers in single layers on large baking sheets and bake in a 350°F oven until hot and crisp, about 15 minutes.