Please solve the programming task below using a self-contained code snippet in a markdown code block.

Given an integer array nums which is sorted in ascending order and all of its elements are unique and given also an integer k, return the kth missing number starting from the leftmost number of the array.
 
Please complete the following python code precisely:
```python
class Solution:
    def missingElement(self, nums: List[int], k: int) -> int:
```