Prepare all ingredients as described above: peel and devein the shrimp, shred the lettuce, slice the tomato and jalapeño, and mince the garlic and shallot.
In a bowl, season the shrimp with Cajun seasoning and toss with extra-virgin olive oil until evenly coated.
Preheat a grill or grill pan to medium heat.
In a small bowl, whisk together the mayonnaise, sriracha sauce, Creole mustard, horseradish, Worcestershire sauce, minced shallot, minced garlic, and fresh lemon juice to make the remoulade.
Grill the shrimp for about 2–3 minutes per side, or until they are opaque and cooked through. Cook shrimp to an internal temperature of 145°F (63°C).
Lightly toast the baguette halves on the grill until golden and crisp.
Assemble each po' boy by layering the inside of the baguette with shredded romaine lettuce, tomato slices, jalapeño slices (if using), and grilled shrimp. Drizzle generously with remoulade sauce.
For the sparkling chia fresca, combine all the ingredients. Let sit for 5 minutes for the chia to bloom.
Serve the grilled shrimp po' boys with carrot sticks and hummus and chia fresca. Enjoy!