If your pudding is not setting properly and you're looking for ways to thicken it, there are a few methods you can try. Here are some suggestions based on the search results:

1. Mix in a slurry of cornstarch: One common method is to create a slurry by mixing a small amount of cornstarch with water. Gradually whisk the slurry into the pudding while it's heating. This can help thicken the pudding [1].

2. Add instant tapioca: Another option is to mix a small amount of instant tapioca into the pudding and let it sit for a few minutes. The tapioca will absorb some of the liquid and help thicken the pudding [1].

3. Trial and error: Pudding can be finicky, so it's important to pay attention to the mixing process. Mixing too vigorously can make the pudding watery, while mixing too little can prevent the ingredients from combining properly. Adjusting the mixing technique and following the recipe carefully can help achieve the desired thickness [3].

4. Adding gelatin: Gelatin can be used to thicken pudding. You will need to whisk sugar, milk, and cream together and bring it to a simmer. Then, measure out the appropriate amount of gelatin powder and let it bloom in cold water. Melt the gelatin and slowly pour it into the pudding mix while stirring. Straining the pudding afterward can help remove any undissolved gelatin [3].

5. Using a starch-based thickening agent: Starch-based thickening agents, such as instant flour, can also be used to thicken pudding. Heat the milk and cream mixture on the stove, reserving a portion of it. Combine sugar with the starch-based thickening agent and whisk the cold milk and cream into it. Pour the mixture into the hot milk and continue cooking until thickened. Strain the pudding to remove any lumps of flour [3].

Learn more:

1. How do you thicken pudding that won't set? - Quora
2. Pudding FAIL. Help me fix or salvage my runny pudding? - cooking baking failure | Ask MetaFilter
3. How to Thicken Pudding (Plus What Makes It Watery) - Baking Kneads, LLC