Make the pesto. In a food processor or blender, process peas, olive oil, walnuts, garlic, 1 ounce basil leaves and lemon juice until texture is smooth but slightly grainy. Season with salt and pepper. Set aside.
Place flatbreads on a parchment-lined baking sheet. Top each flatbread with 2 heaping tablespoons pesto; spread evenly over bread. Divide chicken, sundried tomatoes and Dill Havarti Cheese evenly among the flatbreads. Top each with 2 to 3 asparagus spears.
Bake 18 to 20 minutes or until cheese is bubbly and flatbread edges are golden.
Garnish with crushed red pepper flakes and basil, if desired. Serve warm.