Toss the sprouts in the pan, season with a pinch of kosher salt, and cook in the bacon fat over medium heat until they soften and begin to brown in spots, about 4-6 minutes. Sprinkle in the garlic and thyme, and cook for another 3 minutes. Season to taste with salt and pepper. Add the nuts and the reserved bacon, pour in the maple syrup, and give a squeeze of lemon juice. Serve warm or at room temperature.