Preheat oven to 180C. Place baguette slices on a baking tray, drizzle with extra-virgin olive oil, season to taste and bake, turning once, until golden and crisp (3-4 minutes). Set aside.
Heat olive oil in a large frying pan over medium-high heat, add pancetta and cook, turning once, until crisp (2-3 minutes). Transfer to a plate lined with absorbent paper and set aside to cool, reserve pancetta fat in pan.
For warm anchovy dressing, place pan used for pancetta on low heat, add anchovies and cook until broken down (1-2 minutes). Add vinegar, whisk to combine and remove from heat. Add crème fraîche and mustard, whisk to combine, whisk in extra-virgin olive oil, season to taste and set aside.
Arrange cos halves on a serving platter, crumble pancetta and croûtons over, drizzle with warm anchovy dressing, scatter with parmesan and capers, season to taste with pepper and serve.