Soak beans is plenty of water overnight.
Make the herb bouquet: Gather up the fresh thyme and sage. Tie a short bit of kitchen twine around the bundle and knot it. Done!
Set the instant pot to sauté for 30 min. Add the olive oil.
If you don't have a slow cooker with sauté setting don't panic :-) just use a separate pan and transfer when ready).
Add the onions. Season with a pinch of salt. Sauté onions for 3-4 minutes, until soft and fragrant.
Add the garlic, the celery and carrots. Stir well. Sauté everything for 2-3 minutes more and add the beans. Stir well.
Add about 6 cups of water, the bouillon cubes and the fresh herb bouquet. Stir gently.
Set slow cooker to slow for 12 hours.
Wash swiss chard well. Separate leaves from stems. Cut leaves into chunky pieces. Set aside for later.
Every hour try your beans to check on their cooking. When they are nearly done, stir in the chard leaves, they just needs a few minutes until wilted.
Check soup for salt and pepper and adjust to your liking.
Make the halloumi and chard stems
Heat 1 tbsp olive in a frying pan. Cut the halloumi cheese into thick slices, about 5 mm each (3/16 of an inch). Add slices to the frying pan, season with plenty of fresh ground pepper. Fry each slice for 2-3 min, until they have a nice golden color at the edges.
Cut the stems into ¼ inch pieces. Add one tbsp olive oil in a frying pan, add the stalks. Season with salt and pepper. In medium heat sauté stalks for 6-7 min or until soft. Remove from pan in a bowl and set aside.
Serve soup in bowls. Add a spoonful of swiss chard stems on top, sprinkle some chili flakes and serve with a slice of halloumi cheese and hearty crusty bread.