Garam masala paste for butter chicken
Garam masala powder is a spice blend, other than some anti-caking agents it's almost pure spices. Pastes are spices mixed with oil and maybe water and other ingredients like garlic, chili, pepper, tamarind, and others so they aren't an exact equivalent. Taking garam masala paste in particular if you look at patak's product the spices are only 23% of the total weight, the rest is water, oil, garlic powder and tamarind paste. You would need to add 4 tbsps of paste to get the same amount of spice as 1tbsp of garam masala powder, plus you will be getting extra flavors like garlic and tamarind in the mix.