Vegetable Stew (with beef)

For this stew I have combined ideas that I found online with what I had in the fridge. This recipe can easily be done without the beef and as a vegan/vegetarian version.

Vegetable Stew

beef for stews (optional)
oil mustard and dressing
4-5 cups of broth
1/2 can of tomato paste
spices: bay leaves, oregano or basil, pepper, salt
3 carrots, sliced
3 big potatoes, diced
5 celery stems, diced
1 onion, chopped
1 leek, sliced
1 apple, diced
3 tomatoes, diced
1 cup mushrooms, sliced
3 tablespoons of flour
3 table spoons of water
In a large pot, fry the beef in oil, mustard and dressing until done on the outside.
Add broth, tomato paste and spices, bring to a boil and then simmer for 30-60 minutes (I used this time to cut the vegetables). Add carrots, potatoes, celery, onion and leek. Cook until potatoes are soft. Add apple, tomatoes and mushrooms and cook for another 10-15 minutes.
Whisk together flour and water and add to the stew, cook for another 3 minutes until the stew thickens.

Outcome:
- I couldn't taste the mustard and dressing at all and I wonder if they are necessary (I think I would have liked a little mustard taste, so I will try to add more mustard next time).
- The stew had a very strong tomato taste which I wasn't expecting since I only used half a can. I want to try to leave that out next time.
- Another thing I wasn't expecting was that I couldn't taste the celery much. I don't like raw celery and for that reason haven't used it in cooking either. Maybe it was masked by the tomato taste, but in the future I will not avoid it anymore.
- I added the apple because some sites say that it goes well will celery or celery root, but I don't think that one apple made much difference. Maybe it was also masked by the tomato taste.
- What I really liked was how the stew thickened slightly with the flour and water mixture that is added in the end.