Slotted spoons:

Ketzos Hashulchan rules that using a slotted spoon, a perforated serving spoon, to separate solids from a liquid is forbidden since it is a kli borer. This applies when one is using the slotted spoon to remove solids while being interested in the liquid. For example, if one wants to separate vegetables from soup and only drink the broth, it would be forbidden.

However, if one is interested in removing the solids, such as vegetables or meat, to eat them while disregarding the broth, using a slotted spoon would be permitted. In this case, since the solid is sufficiently large, it is not considered part of a taaroves with the liquid. As a result, the slotted spoon is not considered to be performing an act of separating the taaroves.

Shabbos K’Halachah clarifies that this leniency is only applicable if the solids are clearly recognizable and consist of large pieces. If, however, the solid is mushy, it would be considered a taaroves with the liquid, and one would not be permitted to remove the solid from the liquid. Even though one is taking ochel out of pesoles, the spoon in this case is considered a kli borer.

Orchos Shabbos states that it is forbidden even according to Chazon Ish, because the spoon is specifically designed to separate out gravy. This is unlike a teapot, which is primarily made to hold and pour tea. Rav Wosner concurs with this position.

On the other hand, Rav Ovadia Yosef is lenient based on Maharitatz, who argues that there is no borer of a solid from a liquid since it is not normal to remove solids from a liquid with one’s hand. Additionally, a person is not particular about ensuring that all of the liquid drains from the spoon, which supports the lenient position. Shemiras Shabbos K’hilchasah presents a similar rationale.

Sources:

1. Ketzos Hashulchan 125, Badei Hashulchan 28. This is also the opinion of Shabbos K’Halachah 12:15 and 14:17.
2. A slotted spoon is a spoon-like utensil with slots, holes, or other openings in the bowl. These openings allow liquid to pass through while retaining larger solid pieces on the spoon. For example, if one is cooking pasta in a pot of boiling water, they may use a slotted spoon to scoop out some pasta to test if it is done. The water drains through the slots in the spoon, but the pasta remains. This could be an instance of borer since the spoon can be seen as a tool for separating undesirable parts (such as boiling water) from desirable parts (such as pasta).
3. This is the consensus among contemporary poskim. See Rav Wosner (Shevet Halevi 5:58), Ayil Meshulash (7:34), Shabbos K’halachah 12:51, 14:17, and Shabbos Kitchen (p. 160), all of whom agree.
4. Shabbos K’Halachah 14:18.
5. Orchos Shabbos 1:3:(82).
6. Rav Wosner (Shevet Halevi 8:58) agrees.
7. Yalkut Yosef (319:42 v. 3 p. 306), quoting his father. Or Letzion (2:31:10) agrees.
8. Maharitatz 203, discussed in se’if tes zayin.
9. Shemiras Shabbos K’hilchasah (3:58) offers a similar rationale.