Why does the soufflés I bake shrink after I take it out of the oven?

While the soufflés was baking it rises, but when i take it out of the oven it started to shrink, here is the copy of the recipe i used.

Deep Dark Chocolate Souffle

INGREDIENTS:

Halves whole

• 1 tablespoon white sugar

• 1/2 cup HERSHEY®'S Dutch Processed Cocoa

• 1/4 cup all-purpose flour

• 1/4 cup butter, softened

• 1 cup milk

• 1/2 cup white sugar

• 1 teaspoon vanilla extract

• 4 eggs, separated

• 2 tablespoons white sugar

• 6 scoops coffee ice cream

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DIRECTIONS:

1. Heat oven to 350 F. Butter 6-cup souffle dish; coat with 1 tablespoon sugar.

2. Stir together cocoa and flour in medium bowl. Add butter; blend well. Heat milk in medium saucepan until very hot. Reduce heat; add cocoa mixture, beating with whisk until smooth and thick. Remove from heat; stir in 1/2 cup sugar and vanilla. Cool slightly. Add egg yolks, one at a time, beating well after each addition. Cool to room temperature.

3. Beat egg whites in large bow.