Preheat oven to 375°F. Toss bread pieces with olive oil and salt on a baking sheet. Bake for 7 minutes until golden and crispy.
Cook bacon lardons in a skillet over medium heat until crispy, 7-9 minutes. Transfer to paper towels, reserving the fat.
Add minced shallot to bacon fat and cook until soft, 2-3 minutes. Whisk in red wine vinegar and Dijon mustard.
For the poached eggs, bring water to a simmer in a saucepan. Add white vinegar, create a gentle whirlpool, and carefully drop in eggs. Cook 3-4 minutes until whites are set but yolks remain runny.
Toss frisée and lardons in a bowl with warm bacon dressing. Season with salt and pepper.
Divide salad between plates, top with croutons and poached eggs. Finish with a drizzle of olive oil and flaky sea salt if desired.