Cook bacon in a skillet over medium heat for 8 to 10 minutes until crisp. Drain and cool for 2 minutes.
Slice each large croissant horizontally into 3 layers with a serrated knife, keeping the middle layer intact. Mix mayonnaise with Dijon and spread over the filling-facing surfaces.
Layer half the turkey and a lettuce leaf on each bottom layer, then add the middle croissant layers.
Add remaining turkey, bacon and lettuce. Blot tomato slices, season with salt and pepper, lay them over the bacon and close with the croissant tops.
Press gently to settle the layers, cut each sandwich across the middle with a serrated knife and serve immediately.