Melt 6 tablespoons of butter in a large saucepan over medium heat. Once bubbling gently, sprinkle in 1/2 cup of flour and whisk continuously for about 5 minutes until the mixture smells like warm, toasted nuts to remove the raw flour taste.
Stir in 1/2 teaspoon finely ground white pepper and 2 tablespoons concentrated lobster base. Let this savory mixture cook for one additional minute on the stove to wake up the deep flavors.
Slowly pour in the milk and seafood broth in a steady stream while whisking constantly to prevent lumps. Lower the heat slightly, add 2 ounces of the freshly shredded Monterey Jack cheese, and stir gently until the sauce becomes beautifully thick and bubbly. Remove from heat and cool slightly.
Chop the imitation crabmeat lightly and place into a medium glass mixing bowl. Add the drained and rinsed baby shrimp. Pour 1 1/2 cups of the warm sauce into the bowl and gently fold everything together until coated, being careful not to mash the shrimp.
Lay the 10 flour tortillas flat. Scoop 2 to 3 heaping tablespoons of the creamy seafood filling in an even line across the center of each tortilla. Fold one side tightly over the filling, tuck it slightly, and roll snugly.
Place the rolled enchiladas seam-side down in a lightly greased baking dish, side-by-side. Ladle the remaining creamy white sauce generously over all the tortillas, ensuring they are nicely coated end to end.
Sprinkle the rest of your shredded Monterey Jack cheese evenly across the top and add a light dusting of sweet paprika for color.
Bake in a preheated 425-degree F oven for roughly 12 to 14 minutes until the cheese melts entirely and bubbles around the edges (do not over-brown). Let rest for about 5 minutes before serving hot.