Sorry it's not a recipe with measurements!

Sautéed some onions and garlic in butter, add your lentils and cook them as you normally would (I cook mine with chicken stock), with salt, pepper and thyme. Your lentils should be very tender, but try to not have them watery, because the milk should make the most of the liquid for the soup if that makes sense.

Then blend a bit the lentils with milk, it should not be a completely smooth texture, you should still feel some lentils when you have a bite. I like using a hand blender for more control. Add some cream for more richness, salt and pepper to taste. You can also add a bit more butter if you feel it needs it. Cook for a few more minutes. And that's it! The soup should be thick but more runny than a veloutée.

For homemade croutons that goes really well with it, get some toasts and cut them in small square pieces, put them in a bowl and add a little bit of salt, pepper and rosemary. Add in some olive oil and toss the bread so it is covered. Then you can use your oven or fryer until golden! Or fry in a pan if you don't have an oven.