Preheat the oven to 375°F. Add the potatoes to a large pot and cover with cold water. Add a large pinch of salt. Bring the water to a boil. Reduce to a simmer and cook the potatoes for about 8-12 minutes, or until just fork tender.
Meanwhile, lay the bacon onto a sheet pan in an even layer. Bake for about 25-30 minutes, or until crisp. Transfer the bacon to a plate lined with paper towels and allow to drain.
Increase the oven temperature to 450°F. Drain the potatoes and transfer them to a bowl of ice water for a couple of minutes. Once cool, transfer the potatoes to paper towels and let fully dry. Use your hands or a measuring cup to smash the potatoes flat. Transfer them to the sheet pan in the bacon fat. Drizzle olive oil over top to coat them well. Season with a generous pinch of salt. Roast the potatoes for about 20-25 minutes until crisp, flipping halfway through.
Meanwhile, whisk together the sour cream and lemon juice in a small mixing bowl. Stir in the lemon zest, chives, and scallions. Season with salt to taste. Crumble the bacon into small pieces.
Transfer the potatoes to paper towels to drain. Plate them with the sour cream sauce dolloped over top. Garnish with the bacon, freshly grated parmesan, and lots of freshly ground black pepper.
Make the Peach BBQ Sauce: In a blender or food processor, combine all peach sauce ingredients and blend until mixture is a smooth puree. Can be made 24 hours ahead. Cover and chill until ready to use.
Sprinkle pork tenderloins evenly with 2 tsp kosher salt and 1/2 freshly ground black pepper. Place tenderloins in a large Ziploc bag and add 1/2 cup of the peach BBQ sauce to thoroughly coat the meat. Seal airtight and let pork marinate for at least 2 hours, up to overnight.
Divide remaining peach BBQ sauce in half. You’ll use half of it for basting and half for serving.
Grease and heat grill to medium-high heat. Grill pork tenderloins evenly, using tongs to turn every 4 minutes and basting regularly with peach sauce. Once exterior is nicely charred and an instant thermometer reads 145°F at the thickest center portion of pork, it’s done (approx 12-14 min, depending on thickness of pork.) Immediately remove from heat, transfer to cutting board, and let rest 10 minutes (do not slice yet.)
Slice pork into desired pieces and serve with remaining peach BBQ sauce. Enjoy!