How to Make It
Using kitchen twine, tie the thyme and sage sprigs into a bundle. Turn a 6- to 6 1/2-quart slow cooker to low and set the timer for 5 hours and 15 minutes.
Add the butter and cover until the butter melts. Stir in the flour and mix with a wooden spoon until well incorporated and a paste forms. Stir in the chicken stock and half-and-half, cover and cook for 5 minutes. Whisk the mixture until smooth. Add the herbs, then add the next 9 ingredients, up to and including the salt. Cover and cook for 4 hours, stirring after 2 hours.
Stir in the chicken, peas and corn. Cover and cook until the chicken is white throughout, about 1 hour and 15 minutes. Discard the herb bundle. Season the stew with pepper.
Preheat the oven to 375°. Lightly oil a baking sheet. In a food processor, pulse the bread cubes until coarse crumbs form. Transfer to a large bowl. Add the potato chips and Ritz crackers to the processor and pulse until coarse crumbs form; add to the bowl. Stir in the 1/4 cup of oil and all of the remaining ingredients except the poached eggs and garnishes. Spread the mixture on the prepared baking sheet and pat it out to an even 1/4-inch layer with your fingertips. Bake until golden and crisp, about 45 minutes. Transfer to a rack and let cool. Break into 3-by-3-inch pieces.
Serve the chicken stew in bowls, each topped with a poached egg and a piece of crust. Garnish with thyme, parsley and lemon zest.