Crisp bacon in a large skillet over medium heat then remove to a paper towel lined plate to drain. Reserve 3 Tablespoons bacon grease in skillet (add extra virgin olive oil if there's not enough.) Chop or crumble bacon when cool enough to handle.

Meanwhile, use the grating blade attachment on a food processor, mandolin, or very sharp knife to slice brussels sprouts very thin. Add to a large bowl with almonds and bacon then set aside.

To the bacon grease, still over medium heat, add shallots then saute until tender, 2 minutes. Remove skillet from heat then whisk in vinegar, honey, dijon mustard, salt, and pepper (be careful, vinegar may spatter a bit.) Return skillet to heat then whisk until dressing is combined, 30 seconds. Pour over brussels sprouts mixture then toss well to coat. Taste and add salt and pepper if necessary. Add chopped apple then toss again to mix, and then serve.