Place the chicken in the slow cooker. If the breasts vary greatly in size, pound the thicker pieces to an even thickness so they cook at a similar rate.

Whisk together the condensed cream of chicken soup, chicken broth, milk, salt, black pepper, and optional paprika until smooth. Pour this mixture over the chicken.

Add the sliced mushrooms, chopped onion, green bell pepper, and minced garlic around and over the chicken. Cover and cook on LOW for 4 to 5 hours or HIGH for 2 to 3 hours, until the thickest part of the chicken reaches at least 165°F.

Transfer the cooked chicken to a plate. Shred it with two forks or cut it into bite-size pieces, checking that no pieces remain undercooked.

Return the chicken to the slow cooker. Stir in the drained pimientos, frozen peas, and heavy cream or evaporated milk.

Cover and cook on HIGH for 10 to 15 minutes, just until the peas are hot and the sauce is creamy. Avoid a vigorous boil after adding the dairy.

If the sauce is too thin, mix the cornstarch with cold water to make a slurry. Stir it into the slow cooker and cook for another 5 to 10 minutes, until the sauce thickens.

Serve immediately over biscuits, toast, puff pastry shells, egg noodles, rice, or mashed potatoes.