Halve the avocado, remove the pit, and scoop flesh into a small bowl. Add lime juice and 1/2 tsp of the salt. Mash with a fork until mostly smooth but slightly chunky. Taste and add remaining salt and black pepper to taste. Set aside.

Toast bagels

Slice the everything bagels in half and lightly butter the cut sides with the unsalted butter. Toast in a toaster or under a broiler (cut side up) until golden and just crisp, about 2–4 minutes depending on appliance. Remove and set cut sides up on a work surface.

Bacon

Cook bacon

Cook the applewood bacon to crispiness. For stovetop: place bacon in a cold skillet, turn heat to medium, and cook, flipping occasionally, until evenly browned and crisp, 8–12 minutes. Drain on paper towels. For oven: arrange bacon on a foil-lined rimmed sheet and bake at 400°F (200°C) for 12–18 minutes until crisp. Reserve two slices per sandwich, break in half if needed to fit the bagel.

Cheese & Finish

Melt cheese on bagel

Divide shredded cheddar between the four toasted bagel halves (the two bottom halves primarily, plus a light sprinkle on top halves if desired). Place the cheese-topped bagel halves under a broiler or in a 375°F (190°C) oven for 1–3 minutes until the cheese is melted and bubbly. Watch closely to avoid burning.

Assemble sandwiches

Spread about half of the avocado mixture evenly on the bottom cheese-melted bagel halves. Top each with three slices of crispy bacon (or two slices folded), then drizzle about 1/2 teaspoon of chili oil over the bacon on each sandwich for a spicy crunch. Add cilantro leaves if using. Cap with the top bagel halves.

Serve

Cut each assembled bagel in half if desired and serve immediately while warm. Provide extra chili oil and salt/pepper at the table for adjustments.