Heat oven to 425°F. Lightly sprinkle 18x13-inch sheet pan or large cookie sheet with flour.
Unroll pizza dough onto pan; press dough into 17x12-inch rectangle, forming thicker dough edges. Bake 6 to 8 minutes or until just starting to brown.
Meanwhile, in 10-inch nonstick skillet, cook sausage over medium heat 4 to 6 minutes, stirring occasionally, until no longer pink. Remove from skillet to plate; set aside.
In same skillet, cook shallot over medium heat 1 to 2 minutes, stirring frequently, until crisp-tender. Remove from heat.
Evenly spread mustard over partially baked pizza crust to within 1/2 inch from edges. Sprinkle half of the cheese onto pizza crust. Top with sausage, apple slices, shallot and remaining cheese.
Brush edges of crust with beaten egg; sprinkle lightly with salt.
Bake 6 to 8 minutes or until cheese is melted. To serve, top with arugula; cut into 8 slices.
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For best results, work with cold dough directly from refrigerator.