I've been trying to cook at home recently because I wanted to have a special dessert, and. I had tried it at several restaurants, but none of them were good enough for me. I've been trying to cook at home recently because I wanted to have a special dessert. I had tried it at several restaurants, but none of them were good enough for me.

I split it into two sentences since it sounds more natural that way.

I've been trying to cook at home recently because I wanted to have a special dessert, and I had tried it at several restaurants, but none of them were good enough for me. I've been trying to cook at home recently because I wanted to have a special dessert, and I had tried it at several restaurants, but none of them were good enough for me.

While it is not wrong, it is best to avoid long sentences like this for better flow. Suggestion as follow: I've been trying to cook at home recently because I wanted to have a special dessert. I had tried it at several restaurants, but none of them were good enough for me.

更简洁: I've been trying to cook at home recently because I wanted to have a special dessert, and. I had tried it at several restaurants, but none of them were good enough for mesatisfactory. 更简洁: I've been trying to cook at home recently because I wanted a special dessert. I had tried it at several restaurants, but none of them were satisfactory.

They awere either too sweet or not soft enough. They were either too sweet or not soft enough.

It’s better to use past tense here for consistency with the previous sentence.

They awere either too sweet or not soft enough. They were either too sweet or not soft enough.

For tense consistency

They更平滑：Restaurant versions are either too sweet or not soft enoughtoo hard. 更平滑：Restaurant versions are either too sweet or too hard.

The thing is that, I noticed I spent much more time on it than I had expected. The thing is, I noticed I spent much more time on it than I had expected.

In this sentence you could remove "that", but you don't have to. You could also move it to after "I noticed". Keeping "that" makes it sound more like casual speech.

The thing is that I noticed I spent much more time on it than I had expected. The thing is that I noticed I spent much more time on it than I had expected.

Again, yours is not wrong, it is very common to pause after "is" like below: "The thing is, I noticed I spent much more time on it than I had expected."

The thing is that I noticed I spent much more time on it than I had expected.也可能：Unfortunately, I've been spending too much time in the kitchen! 也可能：Unfortunately, I've been spending too much time in the kitchen!

Such is life！! Such is life!