Before starting, preheat the oven to 425˚F. Remove 2 tbsp butter (dbl for 4 ppl) from the fridge and set aside to come up to room temperature. Wash and dry all produce. Arrange bacon strips in a single layer on a parchment-lined baking sheet. Roast bacon in the top of the oven, flipping halfway through, until golden-brown and cooked through, 12-14 min.**Using tongs, transfer bacon to a paper towel-lined plate. Carefully transfer bacon fat to a small heat-proof bowl. Reserve.

Meanwhile, cut potatoes into 1/4-inch rounds. Add potatoes and 1 tbsp oil to another parchment-lined baking sheet. (NOTE: For 4 ppl, use 2 baking sheets, with 1 tbsp oil per sheet.) Season with BBQ Seasoning, salt and pepper, then toss to coat. Roast in the bottom of the oven, flipping halfway through, until tender and golden-brown, 18-20 min. (NOTE: For 4 ppl, roast in the middle and bottom of the oven, rotating sheets halfway through.)

Meanwhile, core, then cut apple into 1/4-inch slices. Add Dijon, whole grain mustard, mayo and honey to a small bowl. Season with salt and pepper, to taste, then stir to combine.

When bacon is done, heat a large non-stick pan over medium-high heat. When the pan is hot, add 1/2 tbsp reserved bacon fat (dbl for 4 ppl), then apples. Sprinkle 1 tsp sugar (dbl for 4 ppl) over apples. Cook, gently stirring occasionally, until apples are lightly caramelized, 2-3 min.Remove the pan from heat.

Meanwhile, halve buns.Arrange buns on an unlined baking sheet, cut-side up. Spread 2 tbsp softened butter (dbl for 4 ppl) on cut sides.Sprinkle cheese over top buns. Toast in the top of the oven until cheese is melted and bottom buns are golden, 4-5 min. (TIP: Keep your eye on buns so they don't burn!)

Spread some honey-mustard mayo on bottom buns, then stack with bacon, apples and spinach. Close with top buns. Halve melts, if desired.Divide melts and potato rounds between plates. Serve remaining honey-mustard mayo alongside for dipping.