How can I improve rich taste of spiced milk tea?
Hmmm.....
Well, I've lived in India for 12 yrs &amp; this is how I make 'masala chai' or 'spiced milk tea' at home &amp; in my restaurant-

2 cups water

1 teaspoon black tea, loose leaf (I use Tokla tea from Nepal)

1 tablespoon grated fresh ginger

10 black peppercorns, coarsely ground

500 ml full fat 'whole' milk 

Sugar to taste

In a stainless steel 3L pot combine tea, water, ginger &amp; black pepper, bring to boil over high heat. Allow to boil for about 2 minutes.

Add milk to boiling tea, again allow to come to a boil. (Watch the pot closely in case the milk begins to foam, if it does foam- stir &amp; decrease heat a little) Allow to simmer uncovered for 6 minutes.

Remove from heat, let stand for 2 minutes. Add sugar to taste if desired &amp; stir. Use a tea strainer to strain into cups to serve. (or serve sugar on the side so people can add sugar to their own tastes)

Some notes-

I think you are trying to make 'tulsi' chai?
Tulsi = Indian holy basil

If so usually the fresh tulsi leaves (around 8-10) are added to the boiling tea mixture with   around 8 green cardamoms, 2 cloves, 1/4 tsp fennel seeds, and a pinch of cumin seeds as I recall. Some Indians dry roast the whole spices to mellow the flavor a bit.

Use spices like fennel, cloves, star anise, cumin sparingly as their strong flavors can take over &amp; give the chai a 'mouthwash' taste which isn't pleasant.