• Preheat the oven to 450º.

Topping

• In a large bowl, whisk together the flour, baking powder, salt, pepper and cayenne pepper. Cut in the butter with a pastry cutter or a fork until it is the size of small peas. Using a fork, mix in the cheese then add cream, stirring with a fork until large clumps form and the flour is incorporated.
• Place on a baking sheet covered in parchment paper and break up into 2 inch clumps. Bake until slightly brown, 10-12 minutes. Set aside.

Filling

• In a large skillet or dutch oven, add 1 tablespoon of oil and heat over medium-high. Add carrots, onions and celery along with a pinch of salt and pepper and cook until onions are translucent and the carrots are slightly soft, about 5 minutes. Remove to a bowl.
• In the same skillet add 1 tablespoon oil and sliced mushrooms, cook until browned and juices have released, about 5 minutes.Add soy sauce and tomato paste and cook an additional minute. Remove to a bowl with the carrots, onions and celery.
• In the same skillet melt 6 tablespoons of butter and cook over medium high heat. Once melted, whisk in flour and cook for a minute. Gradually add the chicken broth and milk whisking constantly until incorporated and thickened. Season with salt and pepper. Remove from the heat and add 2 tablespoons parsley and lemon juice.
• Add the chicken, veggies and peas, if using, to the sauce and stir to combine. Pour into a deep 9 x 13 inch baking dish. Top with the crumble topping and bake for 15 minutes, until the topping is browned and the filling is bubbly.