Heat oven to 350°F. Microwave frozen spinach as directed on box; squeeze to drain. In food processor, place spinach, 1/2 cup of the onions, cream cheese, 1/2 cup of the Gorgonzola cheese, 1/4 teaspoon salt and 1/4 teaspoon pepper. Cover; process 20 to 30 seconds or until smooth.
Lightly spray 10x15-inch pan with sides with Crisco® Original No-Stick Cooking Spray. Unroll dough in pan. Using pizza cutter or sharp knife, cut dough into 4 rectangles. Reserve 1/3 cup of the spinach mixture. Spoon 1/4 cup remaining spinach mixture in center of each rectangle.
Between sheets of plastic wrap or waxed paper, flatten each chicken breast half to 1/2-inch thickness. Place each chicken breast on top of spinach mixture, pressing down slightly. Bring 4 corners of dough together on top of each chicken breast; pinch top and sides to seal. Place seam sides down on pan.
Bake 25 to 35 minutes or until golden brown and thermometer inserted in chicken reads 165°F.
Meanwhile, in 1-quart nonstick saucepan, bring half-and-half to a boil over medium heat. Reduce heat to medium-low; stir in reserved 1/3 cup spinach mixture, remaining 1/2 cup Gorgonzola cheese, 1/3 cup of the remaining onions and 1/2 teaspoon pepper. Serve warm sauce over Wellingtons. Garnish with remaining green onions.