1 large Vidalia or other sweet onion
3 green onions
1 tbsp (15 mL) minced garlic
1/2 tsp (2 mL) salt
1/2 tsp (2 mL) sugar
2 tbsp (30 mL) butter
2 tbsp (30 mL) oil
3/4 cup (175 mL) mayonnaise
3 1/2 cups (875 mL) shredded extra old cheddar, about 200 g, divided
1. Slice Vidalia onion in half, then thinly slice. Separate rings and set aside. You should have about 4 cups (1 L). Slice white parts of green onions and add to rings along with garlic. Sprinkle with salt and sugar. Stir to mix.
2. Heat butter and oil in a large skillet over medium heat. Add onion mixture. Sauté 5 minutes, stirring often, then reduce heat to low. Continue to cook, stirring often, until onions start to caramelize, 20 to 25 minutes.
3. Turn cooked onion mixture onto a chopping board. Finely chop. Put in a large bowl. Thinly slice green onion tops and set aside 2 tbsp (30 mL) for garnish. Stir remainder into cooked onion. Stir in mayonnaise. While stirring, sprinkle in 3 cups (750 mL) shredded cheese.
4. Turn into a shallow ovenproof dish that will hold about 3 cups (750 mL). Roughly smooth the surface. Cover and refrigerate at least until cold, or up to 2 days.
5. About 30 minutes before serving, heat oven to 375°F (191°C).
6. Sprinkle cold onion dip with remaining 1/2 cup (125 mL) cheddar. Place in oven and bake until golden, 30 to 35 minutes. Sprinkle with reserved green onion and serve warm with baguette slices, chips, crackers or vegetables for dipping.