According to the search results, the consistency of Yorkshire pudding batter should be that of heavy cream, so quite runny but not milk-runny. To achieve this consistency, it is suggested to pour half of the liquid in and then slowly add more until the desired consistency is reached. It is also recommended to mix the batter well to ensure lots of bubbles. Resting the batter for about an hour at room temperature before cooking can also help achieve a thicker consistency and a more uniform structure, making it easier for the puddings to rise. However, it is important to note that the consistency of the batter can vary depending on personal preference and the recipe being used.