Preheat oven to 325° and position rack in the middle of the oven.
Toss lamb with 2 tsp of kosher salt. Set aside while pot preheats.
Add 1 ½ Tbsp of the olive oil to a 4.5-5.5 quart dutch oven, set over medium high heat. When wisp of smoke appears, add ½ of the seasoned lamb. Brown lamb on all sides and remove from pot. Repeat with second half of lamb. Remove from pot and set aside.
Lower heat to medium and add remaining 1 Tbsp of olive oil. Add onions and celery and sauté until onions are translucent.
Add tomato paste and stir. Cook for 2 minutes and add garlic. Stir and cook for 20 seconds.
Add brown sugar and stir. Add flour and stir until no dry flour remains.
Add Guinness beer and stir constantly, scraping any brown bits from the bottom of the pot until the mixture thickens and no lumps remain.
Add lamb stock (or beef or chicken stock) and stir to combine.
Add thyme bundle (or dried thyme), bay leaves and ground pepper. Stir and bring to a simmer.
Carefully return browned lamb to the pot along with any accumulated juices. Stir and return to a simmer.
Cover and transfer to the center of a 325° oven for 1 hour.
After one hour, add cubed potatoes and sliced carrots. Stir, cover and return to the oven for 1 more hour or until potatoes and carrots are tender when pierced with a knife.
Remove thyme bundle and bay leaves. Salt and pepper to taste.
Rinse 1 cup frozen baby sweet peas in cold water until defrosted. Add to stew right before serving. (If refrigerating overnight before serving, add peas after you reheat the stew.)
Serve with Guinness bread on the side!

Soups &

Stews

Carrot Dill Bisque

Chicken and Barley Soup

Corn Chowder Four Ways

French Lentil Soup

The Best Creamy Fresh Tomato Soup

Guinness and Lamb Stew

Jambalaya and Collard Green Soup

Spinach Potato Soup

Split Pea Soup with Crispy Ham