Preheat oven to 120°F. Line a baking sheet with parchment.

Pulse cauliflower in a food processor until rice-like. Microwave for 5 minutes. Cool for 10 minutes.

Squeeze excess water from cauliflower using cheesecloth. Spread on baking sheet.

Bake for 8 minutes, then stir and continue baking for 7 minutes.

Remove from oven and cool to dry.

Increase oven temperature to 400°F.

In a bowl, combine cauliflower rice, 1/2 cup cheese, beaten egg, 1/4 teaspoon salt and 1/4 teaspoon pepper. Mix well and press into an 8-inch nonstick pan.

Bake until browned, about 25 minutes.

Cook bacon in a skillet until crispy. Add onion, carrots, and celery; cook until softened (about 5 minutes). Add chicken, cooking until through (about 5 minutes). Stir in peas and mushrooms, cooking until soft (about 5 minutes).

Pour in chicken broth and cream. Season with remaining salt and pepper; stir, simmer until reduced by one-fourth, about 5 minutes. Mix cornstarch and water; add to skillet, stirring until thickened.

Remove crust from oven. Preheat broiler.

Pour chicken mixture into baked crust. Top with remaining cheese.

Broil until browned and bubbling, 5 to 10 minutes. Cool before serving.