Preheat the oven to 400°F.
Toss bread crumbs with 2 teaspoons Dijon mustard, 2 teaspoons olive oil, and mustard seeds in a small bowl until coated. Lay out on a rimmed baking sheet. Bake until golden and crisp, 6 to 8 minutes, stirring once.
Meanwhile, add water to a deep large nonstick skillet to cover the bottom. Add spinach, tossing over high heat until it has wilted, approximately 2 minutes. Transfer to a sieve and press out the liquid. Wipe out skillet; reserve.
Put spinach in a medium saucepan with 3 teaspoons Dijon mustard, the half and half, and chopped thyme. Stir over medium heat until hot, about 3 minutes. Season with freshly ground black pepper. Remove from heat.
Heat remaining 1 tablespoon oil in reserved skillet over medium-high heat. Fry eggs until whites are cooked through, 3 to 4 minutes.
Divide spinach between 2 plates, spreading out as base for eggs. Top with eggs, crumbs, and thyme sprigs.