Combine the garlic, sage, thyme, rosemary, parsley, olive oil, salt and pepper in an airtight bag. Add the chicken and marinate overnight or for at least 4 hours.
Preheat the oven to 450°F.
Roast the chicken on a baking sheet for about 20 minutes, until cooked through. Remove from the oven, cover, and let rest.
Toss the carrots on a baking sheet with the oil, ras el hanout and salt. Roast until tender and lightly browned, 16-18 minutes.
In a large pot, bring the water, milk, butter and salt to a boil. Reduce heat to low and whisk in the polenta. Cook, stirring regularly, for 20 minutes. Fold the feta and cheddar cheese into the polenta and cook for 10 more minutes. Season with salt and pepper.
In a blender, purée the harissa, shallot, garlic, mustard, orange zest, orange juice, sherry vinegar, brown sugar and spices. Combine the oils in a measuring cup and add slowly, with the blender running, to emulsify. When all oil is incorporated add the cilantro and blend to mix. Season with salt and pepper.
To serve, divide the polenta, chicken and carrots between plates. Top with harissa vinaigrette, feta and cilantro.