When Toriel had suggested they bake a pie together, Sans had no idea what to expect, other than the simplicity of taking two things, putting them in a bowl, and mixing them together.  He was not expecting this.  The pie required that butter be browned, cream be boiled, contents to be heated, pie crust to be baked, and other contents measured and mixed all at the same time.  Sans couldn't even reach the oven, much less monitor four different things having to do with the oven at once. 

Toriel soon saw that problem, and moved to fix it.  They agreed that she would work the oven and stove while Sans worked on measuring and mixing everything else.  With that problem fixed, they moved to actually baking the pie. 

It didn't take Sans long to mix everything needed for the pie crust since it was mostly butter, sugar, and small amounts of flour.  It was quickly placed in the oven to bake while the actual pie was prepared.  Toriel acted quickly and efficiently, probably due to her overwhelming knowledge and experience doing this, and it intimidated Sans in some way.  Still, he continued on.  He had measured everything but the cinnamon, but when he proceeded to do so, he tripped over his own foot, which sent both he and the open container of cinnamon to the ground. 

The cinnamon scattered out onto the floor in front of where Sans landed.  Toriel  whipped around to see the spectacle of her temporary roommate lying on the floor with cinnamon spread out on the patch of ground towards his front side.  Thankfully no cinnamon had gotten on his clothes so she wouldn't have to wash them again.  Or at least not that she could see...

"Sans? Are you alright?" She asked him, her tone slightly playful.  Sans was nervous for a second, before he remembered this was Toriel, his friend.  Not his boss.  She wouldn't punish him or hurt him.  "Y-yeah, I'm fine," he answered.  She smiled and giggled some before reaching out to help him up.  He hesitated slightly before reaching out to her as well, gripping her paw tightly. 

The cinnamon in the kitchen had spread out on the floor, and for the time being was swept up as best as possible by Toriel.  Enough cinnamon had stayed in the container to meet the needs of the recipe, despite most of it having been spilled.  Some of the contents on the stove had become slightly overheated, so Toriel turned off the stove and took out the pie crust.  It was a little darker brown than the ones before had been, but it was still edible. 

It didn't take long for the other contents to be mixed in with the cinnamon, and the contents on the stove sorted out.  Once half of the stove mixture was in the other mixing bowl, it went pretty smoothly, other than a splash of bubbling cream almost hitting Sans' bear hand.  After that he had enough sense to place it on a flat surface while he stirred.  After mixing everything together, they poured the custard like mixture into the pie crust and set it in the oven. 

The warm remnants left in the bowl tasted like a type of custard, and the two monsters ended up scraping the bowl clean of anything left in it.  By that time, the pie had finished baking, and could be set out to cool before having to put it in the fridge.  So, without anything else to do, Toriel figured she would teach Sans to clean some, a skill that he would need if he decided to stay. 

Since he was still too short to reach the sink, she got a stool from the room that was 'under renovations', which was basically just a storage room for her extra materials she had little use of, such as the stool.  Standing on it he could easily work in the sink.  He actually worked very quickly on the dishes, washing them with some recognizable level of skill and expertise.  When asked, he explained that his father used to make him do the dishes since he was at work most of the day.  He also mentioned his brother not allowing him to help due to 'the high probability he would break some important dish or miss a spot'. 

She was still trying to be careful of his still slightly healing injuries, so she took it upon herself to clean the floors.  So Sans worked on the dishes while Toriel worked on mopping up the mess of cinnamon that sweeping had not fully cleared.  Between the two of them, cleaning the mess that preparing the pie had left did not take very long at all, so they decided to take a walk around the Ruins to kill some time. 

The Ruins seemed large to Sans at first, but after he started to complete the puzzles, he practically memorized the layout of the place.  None of the traps had been set off yet, and Toriel actually sought his help if taking them down when he got better, if he decided to stay.  She didn't want any of the inhabitants of the Ruins or even a human child, the target of the traps, to be hurt.  By the monsters that they met in the Ruins, it seemed as if the law of 'kill or be killed' had never been put in place.  All of the froggits were extremely kind to him, reaching out to him, even as a complete stranger, with kindness he had never thought could have ever existed in the underground. 

The vegetoids all offered him something to eat, to which he politely refused, saying that he was saving room for the pie that was baking.  The whinsuns were shy, but still manages to smile and wave at him, still a very welcome reaction.  The moldsmols probably didn't understand anything anyone said, but still wiggled at them.  Toriel seemed to take it as a good sign at least, so that was counted as a friendly encounter.  The migosps all wanted to dance, but due to his injuries and both their lack of dancing ability, they declined.  So the monsters danced for them.  The training dummy just sat there, but overall, it was the nicest place Sans had ever seen. 

By the time they reached the end of the Ruins, it had been more than an hour with talking to everyone.  Since they saw no humans in sight over the buttercups, they headed back to the house.  With no distractions from the other inhabitants now and having solved all the puzzles on their walk to the end, it was easy to go past them and reset them. 

Upon arriving at the house, the pie had almost set in the fridge.  So, instead of baking or cleaning, Toriel figured she would ask what Sans knew of cooking.  "Well, it's been a long time since I actually like cooked cooked, but I can still do basic things like make a sandwich.  Had to learn at a pretty young age since dad was hardly around to cook for us, so the duty fell to me.  It didn't change after he, urm, disappeared..." Sans face stared off into space for a moment, caught up in the past, before Toriel spoke again, waking him from his trance.  "Sandwiches it is then."