Correct way to override css for blueprintjs components?

Question

I've created a simple button and styled it via a custom class, but it doesn't work unless i enforce is using !important in the css file. How can I override styling without using !important?

<Button
  className="asset-selector-btn"
  rightIcon="chevron-down"
  text="Pair"
/>

.asset-selector-btn {
  background: #19191a;
  font-size: 24px;
}